diff --git a/src/runtime_stats.h b/src/runtime_stats.h
index 2d2bf0c..55e57ec 100644
--- a/src/runtime_stats.h
+++ b/src/runtime_stats.h
@@ -59,7 +59,7 @@
  * Memory allocation profiler state.  This is used both globally and
  * per-thread.
  */
-struct PACKED RuntimeStats {
+struct PACKED(4) RuntimeStats {
   RuntimeStats() {
     Clear(~0);
   }