diff --git a/src/libregex/re.rs b/src/libregex/re.rs
index 2a1fda06431..ec93a2b5a59 100644
--- a/src/libregex/re.rs
+++ b/src/libregex/re.rs
@@ -585,7 +585,7 @@ impl<'t> Replacer for &'t str {
     }
 }
 
-impl<'t> Replacer for |&Captures|: 't -> String {
+impl<F> Replacer for F where F: FnMut(&Captures) -> String {
     fn reg_replace<'a>(&'a mut self, caps: &Captures) -> CowString<'a> {
         (*self)(caps).into_cow()
     }
@@ -767,7 +767,7 @@ impl<'t> Captures<'t> {
         // How evil can you get?
         // FIXME: Don't use regexes for this. It's completely unnecessary.
         let re = Regex::new(r"(^|[^$]|\b)\$(\w+)").unwrap();
-        let text = re.replace_all(text, |refs: &Captures| -> String {
+        let text = re.replace_all(text, |&mut: refs: &Captures| -> String {
             let (pre, name) = (refs.at(1), refs.at(2));
             format!("{}{}", pre,
                     match from_str::<uint>(name.as_slice()) {