3 files changed, 9 insertions, 14 deletions
diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index f9e1cb877b6..fd62729cd8f 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1226,14 +1226,11 @@ impl<K, V, S> Debug for HashMap<K, V, S>
     where K: Eq + Hash + Debug, V: Debug, S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{{"));
-
-        for (i, (k, v)) in self.iter().enumerate() {
-            if i != 0 { try!(write!(f, ", ")); }
-            try!(write!(f, "{:?}: {:?}", *k, *v));
+        let mut builder = f.debug_map();
+        for (k, v) in self.iter() {
+            builder = builder.entry(k, v);
         }
-
-        write!(f, "}}")
+        builder.finish()
     }
 }
 
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index 0933b4f662a..44c3d8262a7 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -614,14 +614,11 @@ impl<T, S> fmt::Debug for HashSet<T, S>
           S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{{"));
-
-        for (i, x) in self.iter().enumerate() {
-            if i != 0 { try!(write!(f, ", ")); }
-            try!(write!(f, "{:?}", *x));
+        let mut builder = f.debug_set();
+        for x in self {
+            builder = builder.entry(x);
         }
-
-        write!(f, "}}")
+        builder.finish()
     }
 }
 
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 5f5f2fed567..b7cb8f9ed50 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -128,6 +128,7 @@
 #![feature(into_cow)]
 #![feature(slice_patterns)]
 #![feature(std_misc)]
+#![feature(debug_builders)]
 #![cfg_attr(test, feature(test, rustc_private, std_misc))]
 
 // Don't link to std. We are std.