2 files changed, 5 insertions, 0 deletions
diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index e519d03b..ec93db55 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -91,6 +91,7 @@ tag pat_ {
 tag mutability {
     mut;
     imm;
+    maybe_mut;
 }
 
 tag opacity {
diff --git a/src/comp/front/parser.rs b/src/comp/front/parser.rs
index 71f0f2d8..028b8a31 100644
--- a/src/comp/front/parser.rs
+++ b/src/comp/front/parser.rs
@@ -615,6 +615,10 @@ impure fn parse_path(parser p, greed g) -> ast.path {
 impure fn parse_mutability(parser p) -> ast.mutability {
     if (p.peek() == token.MUTABLE) {
         p.bump();
+        if (p.peek() == token.QUES) {
+            p.bump();
+            ret ast.maybe_mut;
+        }
         ret ast.mut;
     }
     ret ast.imm;