diff --git a/src/librustc/middle/trans/_match.rs b/src/librustc/middle/trans/_match.rs
index 9668f1ec46e3d..88e9adfba0c44 100644
--- a/src/librustc/middle/trans/_match.rs
+++ b/src/librustc/middle/trans/_match.rs
@@ -1155,11 +1155,11 @@ fn store_non_ref_bindings(bcx: @mut Block,
                 let datum = Datum {val: llval, ty: binding_info.ty,
                                    mode: ByRef(ZeroMem)};
                 bcx = datum.store_to(bcx, INIT, lldest);
-                do opt_temp_cleanups.mutate |temp_cleanups| {
+                opt_temp_cleanups.mutate(|temp_cleanups| {
                     add_clean_temp_mem(bcx, lldest, binding_info.ty);
                     temp_cleanups.push(lldest);
                     temp_cleanups
-                }
+                });
             }
             TrByRef => {}
         }
diff --git a/src/libstd/option.rs b/src/libstd/option.rs
index 6e4880550ebb4..7a184a549506a 100644
--- a/src/libstd/option.rs
+++ b/src/libstd/option.rs
@@ -237,19 +237,25 @@ impl<T> Option<T> {
         self.take().map_consume_default(def, blk)
     }
 
-    /// Apply a function to the contained value or do nothing
-    pub fn mutate(&mut self, f: &fn(T) -> T) {
+    /// Apply a function to the contained value and return true, or return false
+    pub fn mutate(&mut self, f: &fn(T) -> T) -> bool {
         if self.is_some() {
             *self = Some(f(self.take_unwrap()));
+            return true;
+        } else {
+            return false;
         }
     }
 
-    /// Apply a function to the contained value or set it to a default
-    pub fn mutate_default(&mut self, def: T, f: &fn(T) -> T) {
+    /// Apply a function to the contained value and return true,
+    /// or set it to a default and return false
+    pub fn mutate_default(&mut self, def: T, f: &fn(T) -> T) -> bool {
         if self.is_some() {
             *self = Some(f(self.take_unwrap()));
+            return true;
         } else {
             *self = Some(def);
+            return false;
         }
     }