diff --git a/js/xpconnect/src/XPCJSID.cpp b/js/xpconnect/src/XPCJSID.cpp
index fba9f6a69d81..f2ad4b25e53b 100644
--- a/js/xpconnect/src/XPCJSID.cpp
+++ b/js/xpconnect/src/XPCJSID.cpp
@@ -260,10 +260,22 @@ NS_IMPL_THREADSAFE_RELEASE(SharedScriptableHelperForJSIID)
 #include "xpc_map_end.h" /* This will #undef the above */
 
 static nsIXPCScriptable* gSharedScriptableHelperForJSIID;
+static bool gClassObjectsWereInited = false;
+
+static void EnsureClassObjectsInitialized()
+{
+    if (!gClassObjectsWereInited) {
+        gSharedScriptableHelperForJSIID = new SharedScriptableHelperForJSIID();
+        NS_ADDREF(gSharedScriptableHelperForJSIID);
+
+        gClassObjectsWereInited = true;
+    }
+}
 
 NS_METHOD GetSharedScriptableHelperForJSIID(PRUint32 language,
                                             nsISupports **helper)
 {
+    EnsureClassObjectsInitialized();
     if (language == nsIProgrammingLanguage::JAVASCRIPT) {
         NS_IF_ADDREF(gSharedScriptableHelperForJSIID);
         *helper = gSharedScriptableHelperForJSIID;
@@ -274,8 +286,6 @@ NS_METHOD GetSharedScriptableHelperForJSIID(PRUint32 language,
 
 /******************************************************/
 
-static JSBool gClassObjectsWereInited = false;
-
 #define NULL_CID                                                              \
 { 0x00000000, 0x0000, 0x0000,                                                 \
   { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } }
@@ -287,22 +297,15 @@ NS_IMPL_CLASSINFO(nsJSIID, GetSharedScriptableHelperForJSIID,
 NS_DECL_CI_INTERFACE_GETTER(nsJSCID)
 NS_IMPL_CLASSINFO(nsJSCID, NULL, nsIClassInfo::THREADSAFE, NULL_CID)
 
-void xpc_InitJSxIDClassObjects()
-{
-    if (!gClassObjectsWereInited) {
-        gSharedScriptableHelperForJSIID = new SharedScriptableHelperForJSIID();
-        NS_ADDREF(gSharedScriptableHelperForJSIID);
-    }
-    gClassObjectsWereInited = true;
-}
-
 void xpc_DestroyJSxIDClassObjects()
 {
-    NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSIID));
-    NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSCID));
-    NS_IF_RELEASE(gSharedScriptableHelperForJSIID);
+    if (gClassObjectsWereInited) {
+        NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSIID));
+        NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSCID));
+        NS_IF_RELEASE(gSharedScriptableHelperForJSIID);
 
-    gClassObjectsWereInited = false;
+        gClassObjectsWereInited = false;
+    }
 }
 
 /***************************************************************************/
diff --git a/js/xpconnect/src/nsXPConnect.cpp b/js/xpconnect/src/nsXPConnect.cpp
index 950d94a8fe19..37bca850f790 100644
--- a/js/xpconnect/src/nsXPConnect.cpp
+++ b/js/xpconnect/src/nsXPConnect.cpp
@@ -1082,8 +1082,6 @@ nsXPConnect::InitClasses(JSContext * aJSContext, JSObject * aGlobalJSObj)
     if (!ac.enter(ccx, aGlobalJSObj))
         return UnexpectedFailure(NS_ERROR_FAILURE);
 
-    xpc_InitJSxIDClassObjects();
-
     XPCWrappedNativeScope* scope =
         XPCWrappedNativeScope::GetNewOrUsed(ccx, aGlobalJSObj);
 
diff --git a/js/xpconnect/src/xpcprivate.h b/js/xpconnect/src/xpcprivate.h
index b75e79188ac4..2faf0dda3197 100644
--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -3493,10 +3493,10 @@ private:
 * member (as a hidden implementaion detail) to which they delegate many calls.
 */
 
-extern void xpc_InitJSxIDClassObjects();
+// Initialization is done on demand, and calling the destructor below is always
+// safe.
 extern void xpc_DestroyJSxIDClassObjects();
 
-
 class nsJSID : public nsIJSID
 {
 public: