diff --git a/runtime/gc/allocator/rosalloc.h b/runtime/gc/allocator/rosalloc.h
index a472a8b..b12cb5b 100644
--- a/runtime/gc/allocator/rosalloc.h
+++ b/runtime/gc/allocator/rosalloc.h
@@ -192,6 +192,7 @@
         Verify();
       }
       DCHECK(slot != nullptr);
+      DCHECK(slot->Next() == nullptr);
       Slot** headp = reinterpret_cast<Slot**>(&head_);
       Slot** tailp = kUseTail ? reinterpret_cast<Slot**>(&tail_) : nullptr;
       Slot* old_head = *headp;