--- a/dom/plugins/PluginModuleChild.cpp
+++ b/dom/plugins/PluginModuleChild.cpp
@@ -1583,16 +1583,26 @@ PluginModuleChild::DeallocNPObject(NPObj
 PLDHashOperator
 PluginModuleChild::DeallocForInstance(NPObjectData* d, void* userArg)
 {
     if (d->instance == static_cast<PluginInstanceChild*>(userArg)) {
         NPObject* o = d->GetKey();
         if (o->_class && o->_class->invalidate)
             o->_class->invalidate(o);
 
+#ifdef NS_BUILD_REFCNT_LOGGING
+        {
+            int32_t refCnt = o->referenceCount;
+            while (refCnt) {
+                --refCnt;
+                NS_LOG_RELEASE(o, refCnt, "NPObject");
+            }
+        }
+#endif
+
         DeallocNPObject(o);
 
         if (d->actor)
             d->actor->NPObjectDestroyed();
 
         return PL_DHASH_REMOVE;
     }