diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index 0b84c6a0aa77a..eed6215150fdb 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -709,7 +709,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
         self.projection_cache
             .borrow_mut()
-            .commit(projection_cache_snapshot);
+            .commit(&projection_cache_snapshot);
         self.type_variables
             .borrow_mut()
             .commit(type_snapshot);
diff --git a/src/librustc/traits/project.rs b/src/librustc/traits/project.rs
index 1ce60d8f05599..5a95b27e93c92 100644
--- a/src/librustc/traits/project.rs
+++ b/src/librustc/traits/project.rs
@@ -1668,15 +1668,15 @@ impl<'tcx> ProjectionCache<'tcx> {
     }
 
     pub fn rollback_to(&mut self, snapshot: ProjectionCacheSnapshot) {
-        self.map.rollback_to(snapshot.snapshot);
+        self.map.rollback_to(&snapshot.snapshot);
     }
 
     pub fn rollback_skolemized(&mut self, snapshot: &ProjectionCacheSnapshot) {
         self.map.partial_rollback(&snapshot.snapshot, &|k| k.ty.has_re_skol());
     }
 
-    pub fn commit(&mut self, snapshot: ProjectionCacheSnapshot) {
-        self.map.commit(snapshot.snapshot);
+    pub fn commit(&mut self, snapshot: &ProjectionCacheSnapshot) {
+        self.map.commit(&snapshot.snapshot);
     }
 
     /// Try to start normalize `key`; returns an error if
diff --git a/src/librustc_data_structures/snapshot_map/mod.rs b/src/librustc_data_structures/snapshot_map/mod.rs
index 6ee8c3579f543..5030bf98dffd5 100644
--- a/src/librustc_data_structures/snapshot_map/mod.rs
+++ b/src/librustc_data_structures/snapshot_map/mod.rs
@@ -92,7 +92,7 @@ impl<K, V> SnapshotMap<K, V>
     pub fn snapshot(&mut self) -> Snapshot {
         self.undo_log.push(UndoLog::OpenSnapshot);
         let len = self.undo_log.len() - 1;
-        Snapshot { len: len }
+        Snapshot { len }
     }
 
     fn assert_open_snapshot(&self, snapshot: &Snapshot) {
@@ -103,8 +103,8 @@ impl<K, V> SnapshotMap<K, V>
         });
     }
 
-    pub fn commit(&mut self, snapshot: Snapshot) {
-        self.assert_open_snapshot(&snapshot);
+    pub fn commit(&mut self, snapshot: &Snapshot) {
+        self.assert_open_snapshot(snapshot);
         if snapshot.len == 0 {
             // The root snapshot.
             self.undo_log.truncate(0);
@@ -135,8 +135,8 @@ impl<K, V> SnapshotMap<K, V>
         }
     }
 
-    pub fn rollback_to(&mut self, snapshot: Snapshot) {
-        self.assert_open_snapshot(&snapshot);
+    pub fn rollback_to(&mut self, snapshot: &Snapshot) {
+        self.assert_open_snapshot(snapshot);
         while self.undo_log.len() > snapshot.len + 1 {
             let entry = self.undo_log.pop().unwrap();
             self.reverse(entry);
diff --git a/src/librustc_data_structures/snapshot_map/test.rs b/src/librustc_data_structures/snapshot_map/test.rs
index 4114082839b0b..b163e0fe420ec 100644
--- a/src/librustc_data_structures/snapshot_map/test.rs
+++ b/src/librustc_data_structures/snapshot_map/test.rs
@@ -20,7 +20,7 @@ fn basic() {
     map.insert(44, "fourty-four");
     assert_eq!(map[&44], "fourty-four");
     assert_eq!(map.get(&33), None);
-    map.rollback_to(snapshot);
+    map.rollback_to(&snapshot);
     assert_eq!(map[&22], "twenty-two");
     assert_eq!(map.get(&33), None);
     assert_eq!(map.get(&44), None);
@@ -33,7 +33,7 @@ fn out_of_order() {
     map.insert(22, "twenty-two");
     let snapshot1 = map.snapshot();
     let _snapshot2 = map.snapshot();
-    map.rollback_to(snapshot1);
+    map.rollback_to(&snapshot1);
 }
 
 #[test]
@@ -43,8 +43,8 @@ fn nested_commit_then_rollback() {
     let snapshot1 = map.snapshot();
     let snapshot2 = map.snapshot();
     map.insert(22, "thirty-three");
-    map.commit(snapshot2);
+    map.commit(&snapshot2);
     assert_eq!(map[&22], "thirty-three");
-    map.rollback_to(snapshot1);
+    map.rollback_to(&snapshot1);
     assert_eq!(map[&22], "twenty-two");
 }