diff --git a/xpcom/base/nsMemoryReporterManager.cpp b/xpcom/base/nsMemoryReporterManager.cpp
index fcdb30ed62ed..b522bdeb7c29 100644
--- a/xpcom/base/nsMemoryReporterManager.cpp
+++ b/xpcom/base/nsMemoryReporterManager.cpp
@@ -1839,7 +1839,7 @@ DEFINE_REGISTER_SIZE_OF_TAB(NonJS);
 namespace mozilla {
 namespace dmd {
 
-class DoNothingCallback : public nsIHandleReportCallback
+class DoNothingCallback MOZ_FINAL : public nsIHandleReportCallback
 {
 public:
     NS_DECL_ISUPPORTS