diff --git a/src/base.rs b/src/base.rs
index 8c19aba1404..5b0aea73a63 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -9,6 +9,10 @@ pub fn trans_mono_item<'a, 'tcx: 'a>(cx: &mut CodegenCx<'a, 'tcx, CurrentBackend
                 def: InstanceDef::Item(def_id),
                 substs,
             } => {
+                let mut mir = ::std::io::Cursor::new(Vec::new());
+                ::rustc_mir::util::write_mir_pretty(tcx, Some(def_id), &mut mir).unwrap();
+                tcx.sess.warn(&format!("{:?}:\n\n{}", def_id, String::from_utf8_lossy(&mir.into_inner())));
+
                 let sig = tcx.fn_sig(def_id);
                 let sig = cton_sig_from_fn_sig(tcx, sig, substs);
                 let func_id = {
@@ -23,10 +27,6 @@ pub fn trans_mono_item<'a, 'tcx: 'a>(cx: &mut CodegenCx<'a, 'tcx, CurrentBackend
 
                 let mut f = Function::with_name_signature(ExternalName::user(0, func_id.index() as u32), sig);
 
-                let mut mir = ::std::io::Cursor::new(Vec::new());
-                ::rustc_mir::util::write_mir_pretty(tcx, Some(def_id), &mut mir).unwrap();
-                tcx.sess.warn(&format!("{:?}:\n\n{}", def_id, String::from_utf8_lossy(&mir.into_inner())));
-
                 ::base::trans_fn(cx, &mut f, inst);
 
                 let mut cton = String::new();
diff --git a/src/common.rs b/src/common.rs
index eedd81d2efc..2be8bf83751 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -47,6 +47,7 @@ fn cton_type_from_ty(ty: Ty) -> Option<types::Type> {
         }
         TypeVariants::TyFnPtr(_) => types::I64,
         TypeVariants::TyRef(..) | TypeVariants::TyRawPtr(..) => types::I64,
+        TypeVariants::TyParam(_)  => bug!("{:?}", ty),
         _ => return None,
     })
 }