diff --git a/mozilla/modules/plugin/base/public/npruntime.h b/mozilla/modules/plugin/base/public/npruntime.h
index 14047c41fee..dc53d5fed09 100644
--- a/mozilla/modules/plugin/base/public/npruntime.h
+++ b/mozilla/modules/plugin/base/public/npruntime.h
@@ -274,7 +274,7 @@ int32_t NPN_IntFromIdentifier(NPIdentifier identifier);
     The NPVariant *result argument of these functions (where
     applicable) should be released using NPN_ReleaseVariantValue().
 */
-typedef NPObject *(*NPAllocateFunctionPtr)(NPP npp);
+typedef NPObject *(*NPAllocateFunctionPtr)(NPP npp, NPClass *aClass);
 typedef void (*NPDeallocateFunctionPtr)(NPObject *npobj);
 typedef void (*NPInvalidateFunctionPtr)(NPObject *npobj);
 typedef bool (*NPHasMethodFunctionPtr)(NPObject *npobj, NPIdentifier name);
diff --git a/mozilla/modules/plugin/base/src/ns4xPlugin.cpp b/mozilla/modules/plugin/base/src/ns4xPlugin.cpp
index bdd4dabadfb..fe3a11f707c 100644
--- a/mozilla/modules/plugin/base/src/ns4xPlugin.cpp
+++ b/mozilla/modules/plugin/base/src/ns4xPlugin.cpp
@@ -1466,7 +1466,7 @@ _createobject(NPP npp, NPClass* aClass)
   NPObject *npobj;
 
   if (aClass->allocate) {
-    npobj = aClass->allocate(npp);
+    npobj = aClass->allocate(npp, aClass);
   } else {
     npobj = (NPObject *)PR_Malloc(sizeof(NPObject));
   }
diff --git a/mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp b/mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
index e640a8040f1..5af38839a6e 100644
--- a/mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
+++ b/mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
@@ -388,8 +388,11 @@ nsJSObjWrapper::~nsJSObjWrapper()
 
 // static
 NPObject *
-nsJSObjWrapper::NP_Allocate(NPP npp)
+nsJSObjWrapper::NP_Allocate(NPP npp, NPClass *aClass)
 {
+  NS_ASSERTION(aClass == &sJSObjWrapperNPClass,
+               "Huh, wrong class passed to NP_Allocate()!!!");
+
   return new nsJSObjWrapper(npp);
 }
 
diff --git a/mozilla/modules/plugin/base/src/nsJSNPRuntime.h b/mozilla/modules/plugin/base/src/nsJSNPRuntime.h
index 86e83209ae6..daa19a77673 100644
--- a/mozilla/modules/plugin/base/src/nsJSNPRuntime.h
+++ b/mozilla/modules/plugin/base/src/nsJSNPRuntime.h
@@ -73,7 +73,7 @@ protected:
   nsJSObjWrapper(NPP npp);
   ~nsJSObjWrapper();
 
-  static NPObject * NP_Allocate(NPP npp);
+  static NPObject * NP_Allocate(NPP npp, NPClass *aClass);
   static void NP_Deallocate(NPObject *obj);
   static void NP_Invalidate(NPObject *obj);
   static bool NP_HasMethod(NPObject *, NPIdentifier identifier);