diff --git a/src/librustc/metadata/tydecode.rs b/src/librustc/metadata/tydecode.rs
index 0e57341a559..b5456e724d2 100644
--- a/src/librustc/metadata/tydecode.rs
+++ b/src/librustc/metadata/tydecode.rs
@@ -465,9 +465,12 @@ fn parse_ty(st: &mut PState, conv: conv_did) -> ty::t {
           return ty::mk_struct(st.tcx, did, substs);
       }
       'k' => {
+          assert_eq!(next(st), '[');
           let did = parse_def(st, NominalType, |x,y| conv(x,y));
-          let region = parse_region(st, conv);
-          return ty::mk_unboxed_closure(st.tcx, did, region);
+          let region = parse_region(st, |x,y| conv(x,y));
+          let substs = parse_substs(st, |x,y| conv(x,y));
+          assert_eq!(next(st), ']');
+          return ty::mk_unboxed_closure(st.tcx, did, region, substs);
       }
       'e' => {
           return ty::mk_err();
diff --git a/src/librustc/metadata/tyencode.rs b/src/librustc/metadata/tyencode.rs
index e11385654cc..6c59537b377 100644
--- a/src/librustc/metadata/tyencode.rs
+++ b/src/librustc/metadata/tyencode.rs
@@ -285,9 +285,11 @@ fn enc_sty(w: &mut SeekableMemWriter, cx: &ctxt, st: &ty::sty) {
             enc_substs(w, cx, substs);
             mywrite!(w, "]");
         }
-        ty::ty_unboxed_closure(def, region) => {
-            mywrite!(w, "k{}", (cx.ds)(def));
+        ty::ty_unboxed_closure(def, region, ref substs) => {
+            mywrite!(w, "k[{}|", (cx.ds)(def));
             enc_region(w, cx, region);
+            enc_substs(w, cx, substs);
+            mywrite!(w, "]");
         }
         ty::ty_err => {
             mywrite!(w, "e");
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 08e14e8034e..abdbd80ebf2 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -594,7 +594,7 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
                       };
                       self.cat_upvar(id, span, var_id, fn_node_id, kind, mode, false)
                   }
-                  ty::ty_unboxed_closure(closure_id, _) => {
+                  ty::ty_unboxed_closure(closure_id, _, _) => {
                       let unboxed_closures = self.typer.unboxed_closures().borrow();
                       let kind = (*unboxed_closures)[closure_id].kind;
                       let mode = self.typer.capture_mode(fn_node_id);
diff --git a/src/librustc/middle/traits/select.rs b/src/librustc/middle/traits/select.rs
index 8f1fcf77ee3..2f345e2e619 100644
--- a/src/librustc/middle/traits/select.rs
+++ b/src/librustc/middle/traits/select.rs
@@ -110,7 +110,7 @@ enum Candidate {
     BuiltinCandidate(ty::BuiltinBound),
     ParamCandidate(VtableParamData),
     ImplCandidate(ast::DefId),
-    UnboxedClosureCandidate(/* closure */ ast::DefId),
+    UnboxedClosureCandidate(/* closure */ ast::DefId, Substs),
     ErrorCandidate,
 }
 
@@ -995,8 +995,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         };
 
         let self_ty = self.infcx.shallow_resolve(obligation.self_ty());
-        let closure_def_id = match ty::get(self_ty).sty {
-            ty::ty_unboxed_closure(id, _) => id,
+        let (closure_def_id, substs) = match ty::get(self_ty).sty {
+            ty::ty_unboxed_closure(id, _, ref substs) => (id, substs.clone()),
             ty::ty_infer(ty::TyVar(_)) => {
                 candidates.ambiguous = true;
                 return Ok(());
@@ -1019,7 +1019,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         };
 
         if closure_kind == kind {
-            candidates.vec.push(UnboxedClosureCandidate(closure_def_id));
+            candidates.vec.push(UnboxedClosureCandidate(closure_def_id, substs.clone()));
         }
 
         Ok(())
@@ -1383,7 +1383,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 Ok(If(tys.clone()))
             }
 
-            ty::ty_unboxed_closure(def_id, _) => {
+            ty::ty_unboxed_closure(def_id, _, ref substs) => {
                 // FIXME -- This case is tricky. In the case of by-ref
                 // closures particularly, we need the results of
                 // inference to decide how to reflect the type of each
@@ -1407,7 +1407,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             .map(|freevar| {
                                 let freevar_def_id = freevar.def.def_id();
                                 self.typer.node_ty(freevar_def_id.node)
-                                    .unwrap_or(ty::mk_err())
+                                    .unwrap_or(ty::mk_err()).subst(self.tcx(), substs)
                             })
                             .collect();
                         Ok(If(tys))
@@ -1548,8 +1548,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 Ok(VtableImpl(vtable_impl))
             }
 
-            UnboxedClosureCandidate(closure_def_id) => {
-                try!(self.confirm_unboxed_closure_candidate(obligation, closure_def_id));
+            UnboxedClosureCandidate(closure_def_id, ref substs) => {
+                try!(self.confirm_unboxed_closure_candidate(obligation, closure_def_id, substs));
                 Ok(VtableUnboxedClosure(closure_def_id))
             }
         }
@@ -1646,12 +1646,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
     fn confirm_unboxed_closure_candidate(&mut self,
                                          obligation: &Obligation,
-                                         closure_def_id: ast::DefId)
+                                         closure_def_id: ast::DefId,
+                                         substs: &Substs)
                                          -> Result<(),SelectionError>
     {
-        debug!("confirm_unboxed_closure_candidate({},{})",
+        debug!("confirm_unboxed_closure_candidate({},{},{})",
                obligation.repr(self.tcx()),
-               closure_def_id.repr(self.tcx()));
+               closure_def_id.repr(self.tcx()),
+               substs.repr(self.tcx()));
 
         let closure_type = match self.typer.unboxed_closures().borrow().find(&closure_def_id) {
             Some(closure) => closure.closure_type.clone(),
@@ -1678,7 +1680,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let trait_ref = Rc::new(ty::TraitRef {
             def_id: obligation.trait_ref.def_id,
             substs: Substs::new_trait(
-                vec![arguments_tuple, new_signature.output],
+                vec![arguments_tuple.subst(self.tcx(), substs),
+                     new_signature.output.subst(self.tcx(), substs)],
                 vec![],
                 obligation.self_ty())
         });
@@ -1959,7 +1962,9 @@ impl Repr for Candidate {
         match *self {
             ErrorCandidate => format!("ErrorCandidate"),
             BuiltinCandidate(b) => format!("BuiltinCandidate({})", b),
-            UnboxedClosureCandidate(c) => format!("MatchedUnboxedClosureCandidate({})", c),
+            UnboxedClosureCandidate(c, ref s) => {
+                format!("MatchedUnboxedClosureCandidate({},{})", c, s.repr(tcx))
+            }
             ParamCandidate(ref a) => format!("ParamCandidate({})", a.repr(tcx)),
             ImplCandidate(a) => format!("ImplCandidate({})", a.repr(tcx)),
         }
diff --git a/src/librustc/middle/trans/adt.rs b/src/librustc/middle/trans/adt.rs
index 438bb337e3f..2525da8863f 100644
--- a/src/librustc/middle/trans/adt.rs
+++ b/src/librustc/middle/trans/adt.rs
@@ -176,8 +176,8 @@ fn represent_type_uncached(cx: &CrateContext, t: ty::t) -> Repr {
 
             return Univariant(mk_struct(cx, ftys.as_slice(), packed, t), dtor)
         }
-        ty::ty_unboxed_closure(def_id, _) => {
-            let upvars = ty::unboxed_closure_upvars(cx.tcx(), def_id);
+        ty::ty_unboxed_closure(def_id, _, ref substs) => {
+            let upvars = ty::unboxed_closure_upvars(cx.tcx(), def_id, substs);
             let upvar_types = upvars.iter().map(|u| u.ty).collect::<Vec<_>>();
             return Univariant(mk_struct(cx, upvar_types.as_slice(), false, t),
                               false)
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index b92b9e84a95..a739f6e3db2 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -253,21 +253,19 @@ fn get_extern_rust_fn(ccx: &CrateContext, fn_ty: ty::t, name: &str, did: ast::De
 }
 
 pub fn self_type_for_unboxed_closure(ccx: &CrateContext,
-                                     closure_id: ast::DefId)
+                                     closure_id: ast::DefId,
+                                     fn_ty: ty::t)
                                      -> ty::t {
-    let unboxed_closure_type = ty::mk_unboxed_closure(ccx.tcx(),
-                                                      closure_id,
-                                                      ty::ReStatic);
     let unboxed_closures = ccx.tcx().unboxed_closures.borrow();
     let unboxed_closure = &(*unboxed_closures)[closure_id];
     match unboxed_closure.kind {
         ty::FnUnboxedClosureKind => {
-            ty::mk_imm_rptr(ccx.tcx(), ty::ReStatic, unboxed_closure_type)
+            ty::mk_imm_rptr(ccx.tcx(), ty::ReStatic, fn_ty)
         }
         ty::FnMutUnboxedClosureKind => {
-            ty::mk_mut_rptr(ccx.tcx(), ty::ReStatic, unboxed_closure_type)
+            ty::mk_mut_rptr(ccx.tcx(), ty::ReStatic, fn_ty)
         }
-        ty::FnOnceUnboxedClosureKind => unboxed_closure_type,
+        ty::FnOnceUnboxedClosureKind => fn_ty
     }
 }
 
@@ -285,14 +283,14 @@ pub fn decl_rust_fn(ccx: &CrateContext, fn_ty: ty::t, name: &str) -> ValueRef {
         ty::ty_closure(ref f) => {
             (f.sig.inputs.clone(), f.sig.output, f.abi, Some(Type::i8p(ccx)))
         }
-        ty::ty_unboxed_closure(closure_did, _) => {
+        ty::ty_unboxed_closure(closure_did, _, ref substs) => {
             let unboxed_closures = ccx.tcx().unboxed_closures.borrow();
             let unboxed_closure = &(*unboxed_closures)[closure_did];
             let function_type = unboxed_closure.closure_type.clone();
-            let self_type = self_type_for_unboxed_closure(ccx, closure_did);
+            let self_type = self_type_for_unboxed_closure(ccx, closure_did, fn_ty);
             let llenvironment_type = type_of_explicit_arg(ccx, self_type);
-            (function_type.sig.inputs.clone(),
-             function_type.sig.output,
+            (function_type.sig.inputs.iter().map(|t| t.subst(ccx.tcx(), substs)).collect(),
+             function_type.sig.output.subst(ccx.tcx(), substs),
              RustCall,
              Some(llenvironment_type))
         }
@@ -738,9 +736,9 @@ pub fn iter_structural_ty<'a, 'blk, 'tcx>(cx: Block<'blk, 'tcx>,
               }
           })
       }
-      ty::ty_unboxed_closure(def_id, _) => {
+      ty::ty_unboxed_closure(def_id, _, ref substs) => {
           let repr = adt::represent_type(cx.ccx(), t);
-          let upvars = ty::unboxed_closure_upvars(cx.tcx(), def_id);
+          let upvars = ty::unboxed_closure_upvars(cx.tcx(), def_id, substs);
           for (i, upvar) in upvars.iter().enumerate() {
               let llupvar = adt::trans_field_ptr(cx, &*repr, data_ptr, 0, i);
               cx = f(cx, llupvar, upvar.ty);
@@ -2351,12 +2349,12 @@ pub fn get_fn_llvm_attributes(ccx: &CrateContext, fn_ty: ty::t)
     let (fn_sig, abi, has_env) = match ty::get(fn_ty).sty {
         ty::ty_closure(ref f) => (f.sig.clone(), f.abi, true),
         ty::ty_bare_fn(ref f) => (f.sig.clone(), f.abi, false),
-        ty::ty_unboxed_closure(closure_did, _) => {
+        ty::ty_unboxed_closure(closure_did, _, ref substs) => {
             let unboxed_closures = ccx.tcx().unboxed_closures.borrow();
             let ref function_type = (*unboxed_closures)[closure_did]
                                                     .closure_type;
 
-            (function_type.sig.clone(), RustCall, true)
+            (function_type.sig.subst(ccx.tcx(), substs), RustCall, true)
         }
         _ => ccx.sess().bug("expected closure or function.")
     };
@@ -2371,7 +2369,7 @@ pub fn get_fn_llvm_attributes(ccx: &CrateContext, fn_ty: ty::t)
     // These have an odd calling convention, so we need to manually
     // unpack the input ty's
     let input_tys = match ty::get(fn_ty).sty {
-        ty::ty_unboxed_closure(_, _) => {
+        ty::ty_unboxed_closure(_, _, _) => {
             assert!(abi == RustCall);
 
             match ty::get(fn_sig.inputs[0]).sty {
diff --git a/src/librustc/middle/trans/callee.rs b/src/librustc/middle/trans/callee.rs
index 22fd943b68c..b8895e9486a 100644
--- a/src/librustc/middle/trans/callee.rs
+++ b/src/librustc/middle/trans/callee.rs
@@ -491,7 +491,7 @@ pub fn trans_fn_ref_with_substs(
     };
 
     // If this is an unboxed closure, redirect to it.
-    match closure::get_or_create_declaration_if_unboxed_closure(ccx, def_id) {
+    match closure::get_or_create_declaration_if_unboxed_closure(bcx, def_id) {
         None => {}
         Some(llfn) => return llfn,
     }
diff --git a/src/librustc/middle/trans/closure.rs b/src/librustc/middle/trans/closure.rs
index 94df7fa57db..d4e1473f0e5 100644
--- a/src/librustc/middle/trans/closure.rs
+++ b/src/librustc/middle/trans/closure.rs
@@ -23,6 +23,7 @@ use middle::trans::common::*;
 use middle::trans::datum::{Datum, DatumBlock, Expr, Lvalue, rvalue_scratch_datum};
 use middle::trans::debuginfo;
 use middle::trans::expr;
+use middle::trans::monomorphize::MonoId;
 use middle::trans::type_of::*;
 use middle::trans::type_::Type;
 use middle::ty;
@@ -312,7 +313,8 @@ fn load_unboxed_closure_environment<'blk, 'tcx>(
     }
 
     // Special case for small by-value selfs.
-    let self_type = self_type_for_unboxed_closure(bcx.ccx(), closure_id);
+    let self_type = self_type_for_unboxed_closure(bcx.ccx(), closure_id,
+                                                  node_id_type(bcx, closure_id.node));
     let kind = kind_for_unboxed_closure(bcx.ccx(), closure_id);
     let llenv = if kind == ty::FnOnceUnboxedClosureKind &&
             !arg_is_indirect(bcx.ccx(), self_type) {
@@ -418,15 +420,26 @@ pub fn trans_expr_fn<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 
 /// Returns the LLVM function declaration for an unboxed closure, creating it
 /// if necessary. If the ID does not correspond to a closure ID, returns None.
-pub fn get_or_create_declaration_if_unboxed_closure(ccx: &CrateContext,
-                                                    closure_id: ast::DefId)
-                                                    -> Option<ValueRef> {
+pub fn get_or_create_declaration_if_unboxed_closure<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
+                                                                closure_id: ast::DefId)
+                                                                -> Option<ValueRef> {
+    let ccx = bcx.ccx();
     if !ccx.tcx().unboxed_closures.borrow().contains_key(&closure_id) {
         // Not an unboxed closure.
         return None
     }
 
-    match ccx.unboxed_closure_vals().borrow().find(&closure_id) {
+    let function_type = node_id_type(bcx, closure_id.node);
+    let params = match ty::get(function_type).sty {
+        ty::ty_unboxed_closure(_, _, ref substs) => substs.types.clone(),
+        _ => unreachable!()
+    };
+    let mono_id = MonoId {
+        def: closure_id,
+        params: params
+    };
+
+    match ccx.unboxed_closure_vals().borrow().find(&mono_id) {
         Some(llfn) => {
             debug!("get_or_create_declaration_if_unboxed_closure(): found \
                     closure");
@@ -435,9 +448,7 @@ pub fn get_or_create_declaration_if_unboxed_closure(ccx: &CrateContext,
         None => {}
     }
 
-    let function_type = ty::mk_unboxed_closure(ccx.tcx(),
-                                               closure_id,
-                                               ty::ReStatic);
+    let function_type = node_id_type(bcx, closure_id.node);
     let symbol = ccx.tcx().map.with_path(closure_id.node, |path| {
         mangle_internal_name_by_path_and_seq(path, "unboxed_closure")
     });
@@ -449,9 +460,9 @@ pub fn get_or_create_declaration_if_unboxed_closure(ccx: &CrateContext,
 
     debug!("get_or_create_declaration_if_unboxed_closure(): inserting new \
             closure {} (type {})",
-           closure_id,
+           mono_id,
            ccx.tn().type_to_string(val_ty(llfn)));
-    ccx.unboxed_closure_vals().borrow_mut().insert(closure_id, llfn);
+    ccx.unboxed_closure_vals().borrow_mut().insert(mono_id, llfn);
 
     Some(llfn)
 }
@@ -469,7 +480,7 @@ pub fn trans_unboxed_closure<'blk, 'tcx>(
 
     let closure_id = ast_util::local_def(id);
     let llfn = get_or_create_declaration_if_unboxed_closure(
-        bcx.ccx(),
+        bcx,
         closure_id).unwrap();
 
     let unboxed_closures = bcx.tcx().unboxed_closures.borrow();
diff --git a/src/librustc/middle/trans/context.rs b/src/librustc/middle/trans/context.rs
index 90159389688..64ad88630f4 100644
--- a/src/librustc/middle/trans/context.rs
+++ b/src/librustc/middle/trans/context.rs
@@ -138,7 +138,7 @@ pub struct LocalCrateContext {
     builder: BuilderRef_res,
 
     /// Holds the LLVM values for closure IDs.
-    unboxed_closure_vals: RefCell<DefIdMap<ValueRef>>,
+    unboxed_closure_vals: RefCell<HashMap<MonoId, ValueRef>>,
 
     dbg_cx: Option<debuginfo::CrateDebugContext>,
 
@@ -419,7 +419,7 @@ impl LocalCrateContext {
                 int_type: Type::from_ref(ptr::null_mut()),
                 opaque_vec_type: Type::from_ref(ptr::null_mut()),
                 builder: BuilderRef_res(llvm::LLVMCreateBuilderInContext(llcx)),
-                unboxed_closure_vals: RefCell::new(DefIdMap::new()),
+                unboxed_closure_vals: RefCell::new(HashMap::new()),
                 dbg_cx: dbg_cx,
                 eh_personality: RefCell::new(None),
                 intrinsics: RefCell::new(HashMap::new()),
@@ -689,7 +689,7 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
         self.local.opaque_vec_type
     }
 
-    pub fn unboxed_closure_vals<'a>(&'a self) -> &'a RefCell<DefIdMap<ValueRef>> {
+    pub fn unboxed_closure_vals<'a>(&'a self) -> &'a RefCell<HashMap<MonoId,ValueRef>> {
         &self.local.unboxed_closure_vals
     }
 
diff --git a/src/librustc/middle/trans/debuginfo.rs b/src/librustc/middle/trans/debuginfo.rs
index 3e07eaf9586..3368b2b7765 100644
--- a/src/librustc/middle/trans/debuginfo.rs
+++ b/src/librustc/middle/trans/debuginfo.rs
@@ -190,7 +190,7 @@ use llvm;
 use llvm::{ModuleRef, ContextRef, ValueRef};
 use llvm::debuginfo::*;
 use metadata::csearch;
-use middle::subst;
+use middle::subst::{mod, Subst};
 use middle::trans::adt;
 use middle::trans::common::*;
 use middle::trans::machine;
@@ -460,9 +460,9 @@ impl TypeMap {
                                                         closure_ty.clone(),
                                                         &mut unique_type_id);
             },
-            ty::ty_unboxed_closure(ref def_id, _) => {
+            ty::ty_unboxed_closure(ref def_id, _, ref substs) => {
                 let closure_ty = cx.tcx().unboxed_closures.borrow()
-                                   .find(def_id).unwrap().closure_type.clone();
+                                   .find(def_id).unwrap().closure_type.subst(cx.tcx(), substs);
                 self.get_unique_type_id_of_closure_type(cx,
                                                         closure_ty,
                                                         &mut unique_type_id);
@@ -2911,9 +2911,9 @@ fn type_metadata(cx: &CrateContext,
         ty::ty_closure(ref closurety) => {
             subroutine_type_metadata(cx, unique_type_id, &closurety.sig, usage_site_span)
         }
-        ty::ty_unboxed_closure(ref def_id, _) => {
+        ty::ty_unboxed_closure(ref def_id, _, ref substs) => {
             let sig = cx.tcx().unboxed_closures.borrow()
-                        .find(def_id).unwrap().closure_type.sig.clone();
+                        .find(def_id).unwrap().closure_type.sig.subst(cx.tcx(), substs);
             subroutine_type_metadata(cx, unique_type_id, &sig, usage_site_span)
         }
         ty::ty_struct(def_id, ref substs) => {
diff --git a/src/librustc/middle/trans/meth.rs b/src/librustc/middle/trans/meth.rs
index 24b41fe144a..bab11c30204 100644
--- a/src/librustc/middle/trans/meth.rs
+++ b/src/librustc/middle/trans/meth.rs
@@ -344,13 +344,10 @@ fn trans_monomorphized_callee<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
             Callee { bcx: bcx, data: Fn(llfn) }
         }
         traits::VtableUnboxedClosure(closure_def_id) => {
-          // The static region and type parameters are lies, but we're in
-          // trans so it doesn't matter.
-          //
-          // FIXME(pcwalton): Is this true in the case of type parameters?
-          let callee_substs = get_callee_substitutions_for_unboxed_closure(
+            let self_ty = node_id_type(bcx, closure_def_id.node);
+            let callee_substs = get_callee_substitutions_for_unboxed_closure(
                 bcx,
-                closure_def_id);
+                self_ty);
 
             let llfn = trans_fn_ref_with_substs(bcx,
                                                 closure_def_id,
@@ -504,24 +501,22 @@ pub fn trans_trait_callee_from_llval<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
     };
 }
 
-/// Creates the self type and (fake) callee substitutions for an unboxed
-/// closure with the given def ID. The static region and type parameters are
-/// lies, but we're in trans so it doesn't matter.
+/// Looks up the substitutions for an unboxed closure and adds the
+/// self type
 fn get_callee_substitutions_for_unboxed_closure(bcx: Block,
-                                                def_id: ast::DefId)
+                                                self_ty: ty::t)
                                                 -> subst::Substs {
-    let self_ty = ty::mk_unboxed_closure(bcx.tcx(), def_id, ty::ReStatic);
-    subst::Substs::erased(
-        VecPerParamSpace::new(Vec::new(),
-                              vec![
-                                  ty::mk_rptr(bcx.tcx(),
-                                              ty::ReStatic,
-                                              ty::mt {
+    match ty::get(self_ty).sty {
+        ty::ty_unboxed_closure(_, _, ref substs) => {
+            substs.with_self_ty(ty::mk_rptr(bcx.tcx(),
+                                            ty::ReStatic,
+                                            ty::mt {
                                                 ty: self_ty,
                                                 mutbl: ast::MutMutable,
-                                              })
-                              ],
-                              Vec::new()))
+                                            }))
+        },
+        _ => unreachable!()
+    }
 }
 
 /// Creates a returns a dynamic vtable for the given type and vtable origin.
@@ -569,10 +564,12 @@ pub fn get_vtable(bcx: Block,
                 emit_vtable_methods(bcx, id, substs).into_iter()
             }
             traits::VtableUnboxedClosure(closure_def_id) => {
+                let self_ty = node_id_type(bcx, closure_def_id.node);
+
                 let callee_substs =
                     get_callee_substitutions_for_unboxed_closure(
                         bcx,
-                        closure_def_id);
+                        self_ty.clone());
 
                 let mut llfn = trans_fn_ref_with_substs(
                     bcx,
@@ -590,25 +587,28 @@ pub fn get_vtable(bcx: Block,
                                                  unboxed closure");
                     if closure_info.kind == ty::FnOnceUnboxedClosureKind {
                         // Untuple the arguments and create an unboxing shim.
-                        let mut new_inputs = vec![
-                            ty::mk_unboxed_closure(bcx.tcx(),
-                                                   closure_def_id,
-                                                   ty::ReStatic)
-                        ];
-                        match ty::get(closure_info.closure_type
-                                                  .sig
-                                                  .inputs[0]).sty {
-                            ty::ty_tup(ref elements) => {
-                                for element in elements.iter() {
-                                    new_inputs.push(*element)
+                        let (new_inputs, new_output) = match ty::get(self_ty).sty {
+                            ty::ty_unboxed_closure(_, _, ref substs) => {
+                                let mut new_inputs = vec![self_ty.clone()];
+                                match ty::get(closure_info.closure_type
+                                              .sig
+                                              .inputs[0]).sty {
+                                    ty::ty_tup(ref elements) => {
+                                        for element in elements.iter() {
+                                            new_inputs.push(element.subst(bcx.tcx(), substs));
+                                        }
+                                    }
+                                    ty::ty_nil => {}
+                                    _ => {
+                                        bcx.tcx().sess.bug("get_vtable(): closure \
+                                                            type wasn't a tuple")
+                                    }
                                 }
-                            }
-                            ty::ty_nil => {}
-                            _ => {
-                                bcx.tcx().sess.bug("get_vtable(): closure \
-                                                    type wasn't a tuple")
-                            }
-                        }
+                                (new_inputs,
+                                 closure_info.closure_type.sig.output.subst(bcx.tcx(), substs))
+                            },
+                            _ => bcx.tcx().sess.bug("get_vtable(): def wasn't an unboxed closure")
+                        };
 
                         let closure_type = ty::BareFnTy {
                             fn_style: closure_info.closure_type.fn_style,
@@ -618,7 +618,7 @@ pub fn get_vtable(bcx: Block,
                                                        .sig
                                                        .binder_id,
                                 inputs: new_inputs,
-                                output: closure_info.closure_type.sig.output,
+                                output: new_output,
                                 variadic: false,
                             },
                         };
diff --git a/src/librustc/middle/trans/type_of.rs b/src/librustc/middle/trans/type_of.rs
index 989ac63cd5c..6d7985767ab 100644
--- a/src/librustc/middle/trans/type_of.rs
+++ b/src/librustc/middle/trans/type_of.rs
@@ -309,11 +309,15 @@ pub fn type_of(cx: &CrateContext, t: ty::t) -> Type {
           let name = llvm_type_name(cx, an_enum, did, tps);
           adt::incomplete_type_of(cx, &*repr, name.as_slice())
       }
-      ty::ty_unboxed_closure(did, _) => {
+      ty::ty_unboxed_closure(did, _, ref substs) => {
           // Only create the named struct, but don't fill it in. We
           // fill it in *after* placing it into the type cache.
           let repr = adt::represent_type(cx, t);
-          let name = llvm_type_name(cx, an_unboxed_closure, did, []);
+          // Unboxed closures can have substitutions in all spaces
+          // inherited from their environment, so we use entire
+          // contents of the VecPerParamSpace to to construct the llvm
+          // name
+          let name = llvm_type_name(cx, an_unboxed_closure, did, substs.types.as_slice());
           adt::incomplete_type_of(cx, &*repr, name.as_slice())
       }
 
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 569c256a738..7fedea67f79 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -962,7 +962,7 @@ pub enum sty {
     ty_closure(Box<ClosureTy>),
     ty_trait(Box<TyTrait>),
     ty_struct(DefId, Substs),
-    ty_unboxed_closure(DefId, Region),
+    ty_unboxed_closure(DefId, Region, Substs),
     ty_tup(Vec<t>),
 
     ty_param(ParamTy), // type parameter
@@ -1636,7 +1636,10 @@ pub fn mk_t(cx: &ctxt, st: sty) -> t {
               flags = flags | HAS_PARAMS;
           }
       }
-      &ty_unboxed_closure(_, ref region) => flags = flags | rflags(*region),
+      &ty_unboxed_closure(_, ref region, ref substs) => {
+          flags = flags | rflags(*region);
+          flags = flags | sflags(substs);
+      }
       &ty_infer(_) => flags = flags | HAS_TY_INFER,
       &ty_enum(_, ref substs) | &ty_struct(_, ref substs) => {
           flags = flags | sflags(substs);
@@ -1885,9 +1888,9 @@ pub fn mk_struct(cx: &ctxt, struct_id: ast::DefId, substs: Substs) -> t {
     mk_t(cx, ty_struct(struct_id, substs))
 }
 
-pub fn mk_unboxed_closure(cx: &ctxt, closure_id: ast::DefId, region: Region)
+pub fn mk_unboxed_closure(cx: &ctxt, closure_id: ast::DefId, region: Region, substs: Substs)
                           -> t {
-    mk_t(cx, ty_unboxed_closure(closure_id, region))
+    mk_t(cx, ty_unboxed_closure(closure_id, region, substs))
 }
 
 pub fn mk_var(cx: &ctxt, v: TyVid) -> t { mk_infer(cx, TyVar(v)) }
@@ -1922,12 +1925,12 @@ pub fn maybe_walk_ty(ty: t, f: |t| -> bool) {
     }
     match get(ty).sty {
         ty_nil | ty_bot | ty_bool | ty_char | ty_int(_) | ty_uint(_) | ty_float(_) |
-        ty_str | ty_infer(_) | ty_param(_) | ty_unboxed_closure(_, _) | ty_err => {}
+        ty_str | ty_infer(_) | ty_param(_) | ty_err => {}
         ty_uniq(ty) | ty_vec(ty, _) | ty_open(ty) => maybe_walk_ty(ty, f),
         ty_ptr(ref tm) | ty_rptr(_, ref tm) => {
             maybe_walk_ty(tm.ty, f);
         }
-        ty_enum(_, ref substs) | ty_struct(_, ref substs) |
+        ty_enum(_, ref substs) | ty_struct(_, ref substs) | ty_unboxed_closure(_, _, ref substs) |
         ty_trait(box TyTrait { ref substs, .. }) => {
             for subty in (*substs).types.iter() {
                 maybe_walk_ty(*subty, |x| f(x));
@@ -2484,10 +2487,10 @@ pub fn type_contents(cx: &ctxt, ty: t) -> TypeContents {
                 apply_lang_items(cx, did, res)
             }
 
-            ty_unboxed_closure(did, r) => {
+            ty_unboxed_closure(did, r, ref substs) => {
                 // FIXME(#14449): `borrowed_contents` below assumes `&mut`
                 // unboxed closure.
-                let upvars = unboxed_closure_upvars(cx, did);
+                let upvars = unboxed_closure_upvars(cx, did, substs);
                 TypeContents::union(upvars.as_slice(),
                                     |f| tc_ty(cx, f.ty, cache)) |
                     borrowed_contents(r, MutMutable)
@@ -2781,8 +2784,8 @@ pub fn is_instantiable(cx: &ctxt, r_ty: t) -> bool {
                 r
             }
 
-            ty_unboxed_closure(did, _) => {
-                let upvars = unboxed_closure_upvars(cx, did);
+            ty_unboxed_closure(did, _, ref substs) => {
+                let upvars = unboxed_closure_upvars(cx, did, substs);
                 upvars.iter().any(|f| type_requires(cx, seen, r_ty, f.ty))
             }
 
@@ -2869,8 +2872,8 @@ pub fn is_type_representable(cx: &ctxt, sp: Span, ty: t) -> Representability {
 
                 find_nonrepresentable(cx, sp, seen, iter)
             }
-            ty_unboxed_closure(did, _) => {
-                let upvars = unboxed_closure_upvars(cx, did);
+            ty_unboxed_closure(did, _, ref substs) => {
+                let upvars = unboxed_closure_upvars(cx, did, substs);
                 find_nonrepresentable(cx, sp, seen, upvars.iter().map(|f| f.ty))
             }
             _ => Representable,
@@ -4225,7 +4228,7 @@ pub fn ty_to_def_id(ty: t) -> Option<ast::DefId> {
         ty_trait(box TyTrait { def_id: id, .. }) |
         ty_struct(id, _) |
         ty_enum(id, _) |
-        ty_unboxed_closure(id, _) => Some(id),
+        ty_unboxed_closure(id, _, _) => Some(id),
         _ => None
     }
 }
@@ -4623,7 +4626,7 @@ pub struct UnboxedClosureUpvar {
 }
 
 // Returns a list of `UnboxedClosureUpvar`s for each upvar.
-pub fn unboxed_closure_upvars(tcx: &ctxt, closure_id: ast::DefId)
+pub fn unboxed_closure_upvars(tcx: &ctxt, closure_id: ast::DefId, substs: &Substs)
                               -> Vec<UnboxedClosureUpvar> {
     if closure_id.krate == ast::LOCAL_CRATE {
         let capture_mode = tcx.capture_modes.borrow().get_copy(&closure_id.node);
@@ -4632,7 +4635,8 @@ pub fn unboxed_closure_upvars(tcx: &ctxt, closure_id: ast::DefId)
             Some(ref freevars) => {
                 freevars.iter().map(|freevar| {
                     let freevar_def_id = freevar.def.def_id();
-                    let mut freevar_ty = node_id_to_type(tcx, freevar_def_id.node);
+                    let freevar_ty = node_id_to_type(tcx, freevar_def_id.node);
+                    let mut freevar_ty = freevar_ty.subst(tcx, substs);
                     if capture_mode == ast::CaptureByRef {
                         let borrow = tcx.upvar_borrow_map.borrow().get_copy(&ty::UpvarId {
                             var_id: freevar_def_id.node,
@@ -5226,7 +5230,7 @@ pub fn hash_crate_independent(tcx: &ctxt, t: t, svh: &Svh) -> u64 {
             ty_open(_) => byte!(22),
             ty_infer(_) => unreachable!(),
             ty_err => byte!(23),
-            ty_unboxed_closure(d, r) => {
+            ty_unboxed_closure(d, r, _) => {
                 byte!(24);
                 did(&mut state, d);
                 region(&mut state, r);
@@ -5503,14 +5507,7 @@ pub fn accumulate_lifetimes_in_type(accumulator: &mut Vec<ty::Region>,
                 ..
             }) |
             ty_struct(_, ref substs) => {
-                match substs.regions {
-                    subst::ErasedRegions => {}
-                    subst::NonerasedRegions(ref regions) => {
-                        for region in regions.iter() {
-                            accumulator.push(*region)
-                        }
-                    }
-                }
+                accum_substs(accumulator, substs);
             }
             ty_closure(ref closure_ty) => {
                 match closure_ty.store {
@@ -5518,7 +5515,10 @@ pub fn accumulate_lifetimes_in_type(accumulator: &mut Vec<ty::Region>,
                     UniqTraitStore => {}
                 }
             }
-            ty_unboxed_closure(_, ref region) => accumulator.push(*region),
+            ty_unboxed_closure(_, ref region, ref substs) => {
+                accumulator.push(*region);
+                accum_substs(accumulator, substs);
+            }
             ty_nil |
             ty_bot |
             ty_bool |
@@ -5537,7 +5537,18 @@ pub fn accumulate_lifetimes_in_type(accumulator: &mut Vec<ty::Region>,
             ty_open(_) |
             ty_err => {}
         }
-    })
+    });
+
+    fn accum_substs(accumulator: &mut Vec<Region>, substs: &Substs) {
+        match substs.regions {
+            subst::ErasedRegions => {}
+            subst::NonerasedRegions(ref regions) => {
+                for region in regions.iter() {
+                    accumulator.push(*region)
+                }
+            }
+        }
+    }
 }
 
 /// A free variable referred to in a function.
diff --git a/src/librustc/middle/ty_fold.rs b/src/librustc/middle/ty_fold.rs
index fa0c29d8883..c7fe8a19937 100644
--- a/src/librustc/middle/ty_fold.rs
+++ b/src/librustc/middle/ty_fold.rs
@@ -534,8 +534,8 @@ pub fn super_fold_sty<'tcx, T: TypeFolder<'tcx>>(this: &mut T,
         ty::ty_struct(did, ref substs) => {
             ty::ty_struct(did, substs.fold_with(this))
         }
-        ty::ty_unboxed_closure(did, ref region) => {
-            ty::ty_unboxed_closure(did, region.fold_with(this))
+        ty::ty_unboxed_closure(did, ref region, ref substs) => {
+            ty::ty_unboxed_closure(did, region.fold_with(this), substs.fold_with(this))
         }
         ty::ty_nil | ty::ty_bot | ty::ty_bool | ty::ty_char | ty::ty_str |
         ty::ty_int(_) | ty::ty_uint(_) | ty::ty_float(_) |
diff --git a/src/librustc/middle/typeck/check/method.rs b/src/librustc/middle/typeck/check/method.rs
index 66693224c87..f8604eeb5c6 100644
--- a/src/librustc/middle/typeck/check/method.rs
+++ b/src/librustc/middle/typeck/check/method.rs
@@ -505,7 +505,7 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
                 }
                 ty_enum(did, _) |
                 ty_struct(did, _) |
-                ty_unboxed_closure(did, _) => {
+                ty_unboxed_closure(did, _, _) => {
                     if self.check_traits == CheckTraitsAndInherentMethods {
                         self.push_inherent_impl_candidates_for_type(did);
                     }
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index 3d1385bac3b..5f6795f24c1 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -3270,7 +3270,8 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
         };
         let closure_type = ty::mk_unboxed_closure(fcx.ccx.tcx,
                                                   local_def(expr.id),
-                                                  region);
+                                                  region,
+                                                  fcx.inh.param_env.free_substs.clone());
         fcx.write_ty(expr.id, closure_type);
 
         check_fn(fcx.ccx,
diff --git a/src/librustc/middle/typeck/check/regionck.rs b/src/librustc/middle/typeck/check/regionck.rs
index deeee67ac6e..8585cacdbc4 100644
--- a/src/librustc/middle/typeck/check/regionck.rs
+++ b/src/librustc/middle/typeck/check/regionck.rs
@@ -867,7 +867,7 @@ fn check_expr_fn_block(rcx: &mut Rcx,
                 }
             });
         }
-        ty::ty_unboxed_closure(_, region) => {
+        ty::ty_unboxed_closure(_, region, _) => {
             if tcx.capture_modes.borrow().get_copy(&expr.id) == ast::CaptureByRef {
                 ty::with_freevars(tcx, expr.id, |freevars| {
                     if !freevars.is_empty() {
@@ -908,7 +908,7 @@ fn check_expr_fn_block(rcx: &mut Rcx,
                 ensure_free_variable_types_outlive_closure_bound(rcx, bounds, expr, freevars);
             })
         }
-        ty::ty_unboxed_closure(_, region) => {
+        ty::ty_unboxed_closure(_, region, _) => {
             ty::with_freevars(tcx, expr.id, |freevars| {
                 let bounds = ty::region_existential_bound(region);
                 ensure_free_variable_types_outlive_closure_bound(rcx, bounds, expr, freevars);
diff --git a/src/librustc/middle/typeck/check/regionmanip.rs b/src/librustc/middle/typeck/check/regionmanip.rs
index a448a93c517..06b633ba15b 100644
--- a/src/librustc/middle/typeck/check/regionmanip.rs
+++ b/src/librustc/middle/typeck/check/regionmanip.rs
@@ -108,7 +108,7 @@ impl<'a, 'tcx> Wf<'a, 'tcx> {
                 self.accumulate_from_closure_ty(ty, c);
             }
 
-            ty::ty_unboxed_closure(_, region) => {
+            ty::ty_unboxed_closure(_, region, _) => {
                 // An "unboxed closure type" is basically
                 // modeled here as equivalent to a struct like
                 //
@@ -118,6 +118,18 @@ impl<'a, 'tcx> Wf<'a, 'tcx> {
                 //
                 // where the `'b` is the lifetime bound of the
                 // contents (i.e., all contents must outlive 'b).
+                //
+                // Even though unboxed closures are glorified structs
+                // of upvars, we do not need to consider them as they
+                // can't generate any new constraints.  The
+                // substitutions on the closure are equal to the free
+                // substitutions of the enclosing parameter
+                // environment.  An upvar captured by value has the
+                // same type as the original local variable which is
+                // already checked for consistency.  If the upvar is
+                // captured by reference it must also outlive the
+                // region bound on the closure, but this is explicitly
+                // handled by logic in regionck.
                 self.push_region_constraint_from_top(region);
             }
 
diff --git a/src/librustc/middle/typeck/coherence/mod.rs b/src/librustc/middle/typeck/coherence/mod.rs
index cb4e878c22c..38ac317b7a3 100644
--- a/src/librustc/middle/typeck/coherence/mod.rs
+++ b/src/librustc/middle/typeck/coherence/mod.rs
@@ -105,7 +105,7 @@ fn get_base_type_def_id(inference_context: &InferCtxt,
             match get(base_type).sty {
                 ty_enum(def_id, _) |
                 ty_struct(def_id, _) |
-                ty_unboxed_closure(def_id, _) => {
+                ty_unboxed_closure(def_id, _, _) => {
                     Some(def_id)
                 }
                 ty_ptr(ty::mt {ty, ..}) |
@@ -445,7 +445,7 @@ impl<'a, 'tcx> CoherenceChecker<'a, 'tcx> {
             match ty::get(self_type.ty).sty {
                 ty::ty_enum(type_def_id, _) |
                 ty::ty_struct(type_def_id, _) |
-                ty::ty_unboxed_closure(type_def_id, _) => {
+                ty::ty_unboxed_closure(type_def_id, _, _) => {
                     tcx.destructor_for_type
                        .borrow_mut()
                        .insert(type_def_id, method_def_id.def_id());
diff --git a/src/librustc/middle/typeck/infer/combine.rs b/src/librustc/middle/typeck/infer/combine.rs
index d2e062a20d2..de59fb80ad5 100644
--- a/src/librustc/middle/typeck/infer/combine.rs
+++ b/src/librustc/middle/typeck/infer/combine.rs
@@ -105,6 +105,15 @@ pub trait Combine<'tcx> {
         } else {
             None
         };
+        self.substs_variances(variances.as_ref().map(|v| &**v), a_subst, b_subst)
+    }
+
+    fn substs_variances(&self,
+                        variances: Option<&ty::ItemVariances>,
+                        a_subst: &subst::Substs,
+                        b_subst: &subst::Substs)
+                        -> cres<subst::Substs>
+    {
         let mut substs = subst::Substs::empty();
 
         for &space in subst::ParamSpace::all().iter() {
@@ -126,7 +135,7 @@ pub trait Combine<'tcx> {
 
                     let mut invariance = Vec::new();
                     let r_variances = match variances {
-                        Some(ref variances) => {
+                        Some(variances) => {
                             variances.regions.get_slice(space)
                         }
                         None => {
@@ -138,7 +147,6 @@ pub trait Combine<'tcx> {
                     };
 
                     let regions = try!(relate_region_params(self,
-                                                            item_def_id,
                                                             r_variances,
                                                             a_regions,
                                                             b_regions));
@@ -150,7 +158,6 @@ pub trait Combine<'tcx> {
         return Ok(substs);
 
         fn relate_region_params<'tcx, C: Combine<'tcx>>(this: &C,
-                                                        item_def_id: ast::DefId,
                                                         variances: &[ty::Variance],
                                                         a_rs: &[ty::Region],
                                                         b_rs: &[ty::Region])
@@ -159,11 +166,9 @@ pub trait Combine<'tcx> {
             let num_region_params = variances.len();
 
             debug!("relate_region_params(\
-                   item_def_id={}, \
                    a_rs={}, \
                    b_rs={},
                    variances={})",
-                   item_def_id.repr(tcx),
                    a_rs.repr(tcx),
                    b_rs.repr(tcx),
                    variances.repr(tcx));
@@ -464,14 +469,15 @@ pub fn super_tys<'tcx, C: Combine<'tcx>>(this: &C, a: ty::t, b: ty::t) -> cres<t
             Ok(ty::mk_struct(tcx, a_id, substs))
       }
 
-      (&ty::ty_unboxed_closure(a_id, a_region),
-       &ty::ty_unboxed_closure(b_id, b_region))
+      (&ty::ty_unboxed_closure(a_id, a_region, ref a_substs),
+       &ty::ty_unboxed_closure(b_id, b_region, ref b_substs))
       if a_id == b_id => {
           // All ty_unboxed_closure types with the same id represent
           // the (anonymous) type of the same closure expression. So
           // all of their regions should be equated.
           let region = try!(this.equate().regions(a_region, b_region));
-          Ok(ty::mk_unboxed_closure(tcx, a_id, region))
+          let substs = try!(this.substs_variances(None, a_substs, b_substs));
+          Ok(ty::mk_unboxed_closure(tcx, a_id, region, substs))
       }
 
       (&ty::ty_uniq(a_inner), &ty::ty_uniq(b_inner)) => {
diff --git a/src/librustc/middle/typeck/variance.rs b/src/librustc/middle/typeck/variance.rs
index d9838cc6444..d8541a54bd9 100644
--- a/src/librustc/middle/typeck/variance.rs
+++ b/src/librustc/middle/typeck/variance.rs
@@ -734,9 +734,8 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 /* leaf type -- noop */
             }
 
-            ty::ty_unboxed_closure(_, region) => {
-                let contra = self.contravariant(variance);
-                self.add_constraints_from_region(region, contra);
+            ty::ty_unboxed_closure(..) => {
+                self.tcx().sess.bug("Unexpected unboxed closure type in variance computation");
             }
 
             ty::ty_rptr(region, ref mt) => {
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 81deae86faa..943570743e8 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -425,7 +425,12 @@ pub fn ty_to_string(cx: &ctxt, typ: t) -> String {
                   bound_str)
       }
       ty_str => "str".to_string(),
-      ty_unboxed_closure(..) => "closure".to_string(),
+      ty_unboxed_closure(ref did, _, ref substs) => {
+          let unboxed_closures = cx.unboxed_closures.borrow();
+          unboxed_closures.find(did).map(|cl| {
+              closure_to_string(cx, &cl.closure_type.subst(cx, substs))
+          }).unwrap_or_else(|| "closure".to_string())
+      }
       ty_vec(t, sz) => {
           match sz {
               Some(n) => {