diff --git a/startupcache/StartupCache.cpp b/startupcache/StartupCache.cpp
index 700b380808..1911fbc053 100644
--- a/startupcache/StartupCache.cpp
+++ b/startupcache/StartupCache.cpp
@@ -725,6 +725,12 @@ StartupCacheWrapper* StartupCacheWrapper::gStartupCacheWrapper = nullptr;
 
 NS_IMPL_ISUPPORTS(StartupCacheWrapper, nsIStartupCache)
 
+StartupCacheWrapper::~StartupCacheWrapper()
+{
+  MOZ_ASSERT(gStartupCacheWrapper == this);
+  gStartupCacheWrapper = nullptr;
+}
+
 StartupCacheWrapper* StartupCacheWrapper::GetSingleton() 
 {
   if (!gStartupCacheWrapper)
diff --git a/startupcache/StartupCache.h b/startupcache/StartupCache.h
index 2086bc3cff..677e44a317 100644
--- a/startupcache/StartupCache.h
+++ b/startupcache/StartupCache.h
@@ -217,7 +217,7 @@ class StartupCacheDebugOutputStream final
 class StartupCacheWrapper final
   : public nsIStartupCache
 {
-  ~StartupCacheWrapper() {}
+  ~StartupCacheWrapper();
 
   NS_DECL_THREADSAFE_ISUPPORTS
   NS_DECL_NSISTARTUPCACHE