--- a/xpcom/components/Module.h
+++ b/xpcom/components/Module.h
@@ -48,17 +48,17 @@ namespace mozilla {
 /**
  * A module implements one or more XPCOM components. This structure is used
  * for both binary and script modules, but the registration members
  * (cids/contractids/categoryentries) are unused for modules which are loaded
  * via a module loader.
  */
 struct Module
 {
-  static const int kVersion = 2;
+  static const unsigned int kVersion = 2;
 
   struct CIDEntry;
 
   typedef already_AddRefed<nsIFactory> (*GetFactoryProcPtr)
     (const Module& module, const CIDEntry& entry);
 
   typedef nsresult (*ConstructorProcPtr)(nsISupports* aOuter,
                                          const nsIID& aIID,

--- a/xpcom/components/nsNativeComponentLoader.cpp
+++ b/xpcom/components/nsNativeComponentLoader.cpp
@@ -199,17 +199,18 @@ nsNativeModuleLoader::LoadModule(nsILoca
 
         free(blist);
     }
 #endif
 
     void *module = PR_FindSymbol(data.library, "NSModule");
     if (module) {
         data.module = *(mozilla::Module const *const *) module;
-        if (mLibraries.Put(hashedFile, data))
+        if (mozilla::Module::kVersion == data.module->mVersion &&
+            mLibraries.Put(hashedFile, data))
             return data.module;
     }
     else {
         LOG(PR_LOG_ERROR,
             ("nsNativeModuleLoader::LoadModule(\"%s\") - "
              "Symbol NSModule not found", filePath.get()));
     }