diff --git a/rust-version b/rust-version
index b1b25c4bcab..7b8f0d43c89 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-84539360498cab3c70a7c9114c0b8106c8e1b06b
+672b272077561ca7b5027a8aff9ea2957c7d4c21
diff --git a/tests/run-pass/heap.rs b/tests/run-pass/heap.rs
index b533f916469..44537e74b5a 100644
--- a/tests/run-pass/heap.rs
+++ b/tests/run-pass/heap.rs
@@ -14,12 +14,12 @@ fn allocate_reallocate() {
     // 6 byte heap alloc (__rust_allocate)
     s.push_str("foobar");
     assert_eq!(s.len(), 6);
-    assert_eq!(s.capacity(), 6);
+    assert_eq!(s.capacity(), 8);
 
     // heap size doubled to 12 (__rust_reallocate)
     s.push_str("baz");
     assert_eq!(s.len(), 9);
-    assert_eq!(s.capacity(), 12);
+    assert_eq!(s.capacity(), 16);
 
     // heap size reduced to 9  (__rust_reallocate)
     s.shrink_to_fit();