diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 27ee9556bd08..06febf33c616 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -818,7 +818,7 @@ pub fn drop<T>(_x: T) { }
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
-    ptr::read(src as *const T as *const U)
+    ptr::read_unaligned(src as *const T as *const U)
 }
 
 /// Opaque type representing the discriminant of an enum.