diff --git a/library/alloc/src/raw_vec.rs b/library/alloc/src/raw_vec.rs
index e00cb361c00..dafbb0acd11 100644
--- a/library/alloc/src/raw_vec.rs
+++ b/library/alloc/src/raw_vec.rs
@@ -494,6 +494,7 @@ where
     alloc_guard(new_layout.size())?;
 
     let memory = if let Some((ptr, old_layout)) = current_memory {
+        debug_assert_eq!(old_layout.align(), new_layout.align());
         unsafe { alloc.grow(ptr, old_layout, new_layout) }
     } else {
         alloc.alloc(new_layout)