diff --git a/dom/base/nsIScriptContext.h b/dom/base/nsIScriptContext.h
index 8f5a279215d..c9e44f6030b 100644
--- a/dom/base/nsIScriptContext.h
+++ b/dom/base/nsIScriptContext.h
@@ -74,8 +74,8 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsIScriptContextPrincipal,
                               NS_ISCRIPTCONTEXTPRINCIPAL_IID)
 
 #define NS_ISCRIPTCONTEXT_IID \
-{ 0x18b25592, 0xb1f3, 0x4e96, \
-  { 0xab, 0x50, 0x3d, 0x91, 0xf4, 0xc8, 0x1d, 0xa1 } }
+{ 0x39b3ea7c, 0xdc26, 0x4756, \
+  { 0xa0, 0x3c, 0x13, 0xa0, 0x42, 0x03, 0x07, 0x6a } }
 
 /* This MUST match JSVERSION_DEFAULT.  This version stuff if we don't
    know what language we have is a little silly... */
@@ -428,7 +428,7 @@ public:
    * call DidInitializeContext() when a context is fully
    * (successfully) initialized.
    */
-  virtual nsresult InitClasses(void *aGlobalObj) = 0;
+  virtual nsresult InitClasses(JSObject* aGlobalObj) = 0;
 
   /**
    * Clear the scope object - may be called either as we are being torn down,
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index d3f43565a61..aa6b2029e09 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -2959,13 +2959,9 @@ static JSFunctionSpec EthogramFunctions[] = {
 #endif
 
 nsresult
-nsJSContext::InitClasses(void *aGlobalObj)
+nsJSContext::InitClasses(JSObject* aGlobalObj)
 {
-  nsresult rv = NS_OK;
-
-  JSObject *globalObj = static_cast<JSObject *>(aGlobalObj);
-
-  rv = InitializeExternalClasses();
+  nsresult rv = InitializeExternalClasses();
   NS_ENSURE_SUCCESS(rv, rv);
 
   JSAutoRequest ar(mContext);
@@ -2973,21 +2969,21 @@ nsJSContext::InitClasses(void *aGlobalObj)
   ::JS_SetOptions(mContext, mDefaultJSOptions);
 
   // Attempt to initialize profiling functions
-  ::JS_DefineProfilingFunctions(mContext, globalObj);
+  ::JS_DefineProfilingFunctions(mContext, aGlobalObj);
 
 #ifdef NS_TRACE_MALLOC
   // Attempt to initialize TraceMalloc functions
-  ::JS_DefineFunctions(mContext, globalObj, TraceMallocFunctions);
+  ::JS_DefineFunctions(mContext, aGlobalObj, TraceMallocFunctions);
 #endif
 
 #ifdef MOZ_JPROF
   // Attempt to initialize JProf functions
-  ::JS_DefineFunctions(mContext, globalObj, JProfFunctions);
+  ::JS_DefineFunctions(mContext, aGlobalObj, JProfFunctions);
 #endif
 
 #ifdef MOZ_TRACEVIS
   // Attempt to initialize Ethogram functions
-  ::JS_DefineFunctions(mContext, globalObj, EthogramFunctions);
+  ::JS_DefineFunctions(mContext, aGlobalObj, EthogramFunctions);
 #endif
 
   JSOptionChangedCallback(js_options_dot_str, this);
diff --git a/dom/base/nsJSEnvironment.h b/dom/base/nsJSEnvironment.h
index 921f7da3ee5..34289426cf8 100644
--- a/dom/base/nsJSEnvironment.h
+++ b/dom/base/nsJSEnvironment.h
@@ -161,7 +161,7 @@ public:
 
   virtual void SetGCOnDestruction(bool aGCOnDestruction);
 
-  virtual nsresult InitClasses(void *aGlobalObj);
+  virtual nsresult InitClasses(JSObject* aGlobalObj);
   virtual void ClearScope(void* aGlobalObj, bool bClearPolluters);
 
   virtual void WillInitializeContext();