diff --git a/dom/base/nsWindowMemoryReporter.h b/dom/base/nsWindowMemoryReporter.h
index dbf38084f063..1691a21402b6 100644
--- a/dom/base/nsWindowMemoryReporter.h
+++ b/dom/base/nsWindowMemoryReporter.h
@@ -47,6 +47,8 @@ public:
       #define ZERO_SIZE(kind, mSize)  mSize(0),
       FOR_EACH_SIZE(ZERO_SIZE)
       #undef ZERO_SIZE
+      mDOMEventTargetsCount(0),
+      mDOMEventListenersCount(0),
       mArenaStats(),
       mMallocSizeOf(aMallocSizeOf)
   {}