diff --git a/src/boot/fe/ast.ml b/src/boot/fe/ast.ml
index 6962a9e08dd..32eed2c14e9 100644
--- a/src/boot/fe/ast.ml
+++ b/src/boot/fe/ast.ml
@@ -410,7 +410,7 @@ and obj =
 and ty_param = ident * (ty_param_idx * effect)
 
 and mod_item' =
-    MOD_ITEM_type of ty
+    MOD_ITEM_type of (effect * ty)
   | MOD_ITEM_tag of (header_tup * ty_tag * node_id)
   | MOD_ITEM_mod of (mod_view * mod_items)
   | MOD_ITEM_fn of fn
@@ -1212,6 +1212,10 @@ and fmt_ident_and_params
   fmt_ident ff id;
   fmt_decl_params ff params
 
+and fmt_effect_qual (ff:Format.formatter) (e:effect) : unit =
+  fmt_effect ff e;
+  if e <> PURE then fmt ff " ";
+
 and fmt_fn
     (ff:Format.formatter)
     (id:ident)
@@ -1219,8 +1223,7 @@ and fmt_fn
     (f:fn)
     : unit =
   fmt_obox ff;
-  fmt_effect ff f.fn_aux.fn_effect;
-  if f.fn_aux.fn_effect <> PURE then fmt ff " ";
+  fmt_effect_qual ff f.fn_aux.fn_effect;
   fmt ff "%s "(if f.fn_aux.fn_is_iter then "iter" else "fn");
   fmt_ident_and_params ff id params;
   fmt_header_slots ff f.fn_input_slots;
@@ -1240,8 +1243,7 @@ and fmt_obj
     (obj:obj)
     : unit =
   fmt_obox ff;
-  fmt_effect ff obj.obj_effect;
-  if obj.obj_effect <> PURE then fmt ff " ";
+  fmt_effect_qual ff obj.obj_effect;
   fmt ff "obj ";
   fmt_ident_and_params ff id params;
   fmt_header_slots ff obj.obj_state;
@@ -1277,7 +1279,8 @@ and fmt_mod_item (ff:Format.formatter) (id:ident) (item:mod_item) : unit =
   let params = Array.map (fun i -> i.node) params in
     begin
       match item.node.decl_item with
-          MOD_ITEM_type ty ->
+          MOD_ITEM_type (e, ty) ->
+            fmt_effect_qual ff e;
             fmt ff "type ";
             fmt_ident_and_params ff id params;
             fmt ff " = ";
diff --git a/src/boot/fe/item.ml b/src/boot/fe/item.ml
index 658fb8c4dde..130909e2fa6 100644
--- a/src/boot/fe/item.ml
+++ b/src/boot/fe/item.ml
@@ -760,6 +760,20 @@ and parse_obj_item
          span ps apos bpos
            (decl params (Ast.MOD_ITEM_obj obj)))
 
+and parse_type_item
+    (ps:pstate)
+    (apos:pos)
+    (effect:Ast.effect)
+    : (Ast.ident * Ast.mod_item) =
+  expect ps TYPE;
+  let (ident, params) = parse_ident_and_params ps "type" in
+  let _ = expect ps EQ in
+  let ty = ctxt "mod type item: ty" Pexp.parse_ty ps in
+  let _ = expect ps SEMI in
+  let bpos = lexpos ps in
+  let item = Ast.MOD_ITEM_type (effect, ty) in
+    (ident, span ps apos bpos (decl params item))
+
 
 and parse_mod_item (ps:pstate) : (Ast.ident * Ast.mod_item) =
   let apos = lexpos ps in
@@ -775,13 +789,15 @@ and parse_mod_item (ps:pstate) : (Ast.ident * Ast.mod_item) =
       | _ -> ps.pstate_infer_lib_name ident
   in
 
+
     match peek ps with
 
-        IO | STATE | UNSAFE | OBJ | FN | ITER ->
+        IO | STATE | UNSAFE | TYPE | OBJ | FN | ITER ->
           let effect = Pexp.parse_effect ps in
             begin
               match peek ps with
                   OBJ -> parse_obj_item ps apos effect
+                | TYPE -> parse_type_item ps apos effect
                 | _ ->
                     let is_iter = (peek ps) = ITER in
                       bump ps;
@@ -795,16 +811,6 @@ and parse_mod_item (ps:pstate) : (Ast.ident * Ast.mod_item) =
                            (decl params (Ast.MOD_ITEM_fn fn)))
             end
 
-      | TYPE ->
-          bump ps;
-          let (ident, params) = parse_ident_and_params ps "type" in
-          let _ = expect ps EQ in
-          let ty = ctxt "mod type item: ty" Pexp.parse_ty ps in
-          let _ = expect ps SEMI in
-          let bpos = lexpos ps in
-          let item = Ast.MOD_ITEM_type ty in
-            (ident, span ps apos bpos (decl params item))
-
       | MOD ->
           bump ps;
           let (ident, params) = parse_ident_and_params ps "mod" in
@@ -964,7 +970,8 @@ and parse_mod_item_from_signature (ps:pstate)
         in
           expect ps SEMI;
           let bpos = lexpos ps in
-            (ident, span ps apos bpos (decl params (Ast.MOD_ITEM_type t)))
+            (ident, span ps apos bpos
+               (decl params (Ast.MOD_ITEM_type (Ast.UNSAFE, t))))
 
     | _ -> raise (unexpected ps)
 
@@ -1008,7 +1015,7 @@ and expand_tags
       | _ -> [| |]
   in
     match item.node.Ast.decl_item with
-        Ast.MOD_ITEM_type tyd -> handle_ty_decl item.id tyd
+        Ast.MOD_ITEM_type (_, tyd) -> handle_ty_decl item.id tyd
       | _ -> [| |]
 
 
diff --git a/src/boot/fe/pexp.ml b/src/boot/fe/pexp.ml
index 1869a7d3a2b..14065466fb8 100644
--- a/src/boot/fe/pexp.ml
+++ b/src/boot/fe/pexp.ml
@@ -360,9 +360,6 @@ and flag (ps:pstate) (tok:token) : bool =
   then (bump ps; true)
   else false
 
-and parse_mutability (ps:pstate) : bool =
-  flag ps MUTABLE
-
 and parse_slot (aliases_ok:bool) (ps:pstate) : Ast.slot =
   let mode =
   match (peek ps, aliases_ok) with
diff --git a/src/boot/me/dwarf.ml b/src/boot/me/dwarf.ml
index 7b54de257d3..5fd8638f4a5 100644
--- a/src/boot/me/dwarf.ml
+++ b/src/boot/me/dwarf.ml
@@ -1210,6 +1210,8 @@ let (abbrev_typedef:abbrev) =
   (DW_TAG_typedef, DW_CHILDREN_yes,
    [|
      (DW_AT_name, DW_FORM_string);
+     (DW_AT_mutable, DW_FORM_flag);
+     (DW_AT_pure, DW_FORM_flag);
      (DW_AT_type, DW_FORM_ref_addr)
    |])
 ;;
@@ -2319,6 +2321,7 @@ let dwarf_visitor
 
   let emit_typedef_die
       (id:Ast.ident)
+      (e:Ast.effect)
       (ty:Ast.ty)
       : unit =
     let abbrev_code = get_abbrev_code abbrev_typedef in
@@ -2327,6 +2330,7 @@ let dwarf_visitor
          uleb abbrev_code;
          (* DW_AT_name: DW_FORM_string *)
          ZSTRING id;
+         encode_effect e;
          (* DW_AT_type: DW_FORM_ref_addr *)
          (ref_type_die ty);
        |])
@@ -2388,13 +2392,13 @@ let dwarf_visitor
                   (Hashtbl.find cx.ctxt_fn_fixups item.id);
                 emit_type_param_decl_dies item.node.Ast.decl_params;
             end
-        | Ast.MOD_ITEM_type _ ->
+        | Ast.MOD_ITEM_type (e, _) ->
             begin
               log cx "walking typedef '%s' with %d type params"
                 (path_name())
                 (Array.length item.node.Ast.decl_params);
               emit_typedef_die
-                id (Hashtbl.find cx.ctxt_all_type_items item.id);
+                id e (Hashtbl.find cx.ctxt_all_type_items item.id);
               emit_type_param_decl_dies item.node.Ast.decl_params;
             end
         | _ -> ()
@@ -3100,9 +3104,10 @@ let rec extract_mod_items
   let die = Hashtbl.find dies i in
     match die.die_tag with
         DW_TAG_typedef ->
+          let effect = get_effect die in
           let ident = get_name die in
           let ty = get_referenced_ty die in
-          let tyi = Ast.MOD_ITEM_type ty in
+          let tyi = Ast.MOD_ITEM_type (effect, ty) in
           let (params, islots) = get_formals die in
             assert ((Array.length islots) = 0);
             htab_put mis ident (decl params tyi)
diff --git a/src/boot/me/resolve.ml b/src/boot/me/resolve.ml
index 72558ae69c7..5077d5cea20 100644
--- a/src/boot/me/resolve.ml
+++ b/src/boot/me/resolve.ml
@@ -270,7 +270,7 @@ let type_reference_and_tag_extracting_visitor
   let visit_mod_item_pre id params item =
     begin
       match item.node.Ast.decl_item with
-          Ast.MOD_ITEM_type ty ->
+          Ast.MOD_ITEM_type (_, ty) ->
             begin
               log cx "extracting references for type node %d"
                 (int_of_node item.id);
@@ -395,7 +395,7 @@ and lookup_type_by_name
     | Some (scopes', id) ->
         let ty, params =
           match htab_search cx.ctxt_all_defns id with
-              Some (DEFN_item { Ast.decl_item = Ast.MOD_ITEM_type t;
+              Some (DEFN_item { Ast.decl_item = Ast.MOD_ITEM_type (_, t);
                                 Ast.decl_params = params }) ->
                 (t, Array.map (fun p -> p.node) params)
             | Some (DEFN_item { Ast.decl_item = Ast.MOD_ITEM_obj ob;
@@ -543,7 +543,7 @@ let type_resolving_visitor
     begin
       try
         match item.node.Ast.decl_item with
-            Ast.MOD_ITEM_type ty ->
+            Ast.MOD_ITEM_type (_, ty) ->
               let ty =
                 resolve_type cx (!scopes) recursive_tag_groups
                   all_tags empty_recur_info ty
@@ -838,7 +838,7 @@ let resolve_recursion
         then begin
           match Hashtbl.find cx.ctxt_all_defns id with
               DEFN_item
-                { Ast.decl_item = Ast.MOD_ITEM_type (Ast.TY_tag _) } ->
+                { Ast.decl_item = Ast.MOD_ITEM_type (_, (Ast.TY_tag _)) } ->
                 log cx "type %d is a recursive tag" (int_of_node id);
                 Hashtbl.replace recursive_tag_types id ()
             | _ ->
diff --git a/src/boot/me/walk.ml b/src/boot/me/walk.ml
index af4a6216a7f..0b60c8320e5 100644
--- a/src/boot/me/walk.ml
+++ b/src/boot/me/walk.ml
@@ -235,7 +235,7 @@ and walk_mod_item
     : unit =
   let children _ =
     match item.node.Ast.decl_item with
-        Ast.MOD_ITEM_type ty -> walk_ty v ty
+        Ast.MOD_ITEM_type (_, ty) -> walk_ty v ty
       | Ast.MOD_ITEM_fn f -> walk_fn v f item.id
       | Ast.MOD_ITEM_tag (htup, ttag, _) ->
           walk_header_tup v htup;