diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 55b34fe81ed5..045720b0268a 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -949,7 +949,7 @@ impl<T: ::fmt::Debug> ::fmt::Debug for ManuallyDrop<T> {
 /// NB: This is very different from the `unreachable!()` macro: Unlike the
 /// macro, which panics when it is executed, it is *undefined behavior* to
 /// reach code marked with this function.
-#[unstable(feature = "unreachable", issue = "0")]
+#[unstable(feature = "unreachable", issue = "43751")]
 pub unsafe fn unreachable() -> ! {
     intrinsics::unreachable()
 }