diff --git a/dom/base/nsIScriptContext.h b/dom/base/nsIScriptContext.h
index 357a11f12e7b..ca7d5e10bd76 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 \
-{ 0x0ffcb42a, 0xd2cf, 0x4e16, \
-  { 0xac, 0x24, 0x5e, 0x7d, 0xd0, 0x71, 0x72, 0x12 } }
+{ 0xace7960f, 0x263b, 0x4a9a, \
+  { 0xaa, 0x1f, 0x87, 0x86, 0x5c, 0x67, 0x03, 0x7f } }
 
 /* This MUST match JSVERSION_DEFAULT.  This version stuff if we don't
    know what language we have is a little silly... */
@@ -121,10 +121,9 @@ public:
                                   nsAString *aRetValue,
                                   bool* aIsUndefined) = 0;
 
-  // Note JS bigotry remains here - 'void *aRetValue' is assumed to be a
-  // jsval.  This must move to JSObject before it can be made agnostic.
+  // 'void *aRetValue' is assumed to be a jsval.
   virtual nsresult EvaluateStringWithValue(const nsAString& aScript,
-                                           void *aScopeObject,
+                                           JSObject* aScopeObject,
                                            nsIPrincipal *aPrincipal,
                                            const char *aURL,
                                            PRUint32 aLineNo,
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 857879364d90..50f37f158a60 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -1196,7 +1196,7 @@ nsJSContext::GetCCRefcnt()
 
 nsresult
 nsJSContext::EvaluateStringWithValue(const nsAString& aScript,
-                                     void *aScopeObject,
+                                     JSObject* aScopeObject,
                                      nsIPrincipal *aPrincipal,
                                      const char *aURL,
                                      PRUint32 aLineNo,
@@ -1207,6 +1207,9 @@ nsJSContext::EvaluateStringWithValue(const nsAString& aScript,
   NS_TIME_FUNCTION_MIN_FMT(1.0, "%s (line %d) (url: %s, line: %d)", MOZ_FUNCTION_NAME,
                            __LINE__, aURL, aLineNo);
 
+  NS_ABORT_IF_FALSE(aScopeObject,
+    "Shouldn't call EvaluateStringWithValue with null scope object.");
+
   NS_ENSURE_TRUE(mIsInitialized, NS_ERROR_NOT_INITIALIZED);
 
   if (!mScriptsEnabled) {
@@ -1217,15 +1220,12 @@ nsJSContext::EvaluateStringWithValue(const nsAString& aScript,
     return NS_OK;
   }
 
-  nsresult rv;
-  if (!aScopeObject)
-    aScopeObject = ::JS_GetGlobalObject(mContext);
-
   // Safety first: get an object representing the script's principals, i.e.,
   // the entities who signed this script, or the fully-qualified-domain-name
   // or "codebase" from which it was loaded.
   JSPrincipals *jsprin;
   nsIPrincipal *principal = aPrincipal;
+  nsresult rv;
   if (!aPrincipal) {
     nsIScriptGlobalObject *global = GetGlobalObject();
     if (!global)
@@ -1277,7 +1277,7 @@ nsJSContext::EvaluateStringWithValue(const nsAString& aScript,
     JSAutoRequest ar(mContext);
 
     JSAutoEnterCompartment ac;
-    if (!ac.enter(mContext, (JSObject *)aScopeObject)) {
+    if (!ac.enter(mContext, aScopeObject)) {
       JSPRINCIPALS_DROP(mContext, jsprin);
       stack->Pop(nsnull);
       return NS_ERROR_FAILURE;
@@ -1286,9 +1286,9 @@ nsJSContext::EvaluateStringWithValue(const nsAString& aScript,
     ++mExecuteDepth;
 
     ok = ::JS_EvaluateUCScriptForPrincipalsVersion(mContext,
-                                                   (JSObject *)aScopeObject,
+                                                   aScopeObject,
                                                    jsprin,
-                                                   (jschar*)PromiseFlatString(aScript).get(),
+                                                   static_cast<const jschar*>(PromiseFlatString(aScript).get()),
                                                    aScript.Length(),
                                                    aURL,
                                                    aLineNo,
diff --git a/dom/base/nsJSEnvironment.h b/dom/base/nsJSEnvironment.h
index 85f3101d16be..8d4affd22e39 100644
--- a/dom/base/nsJSEnvironment.h
+++ b/dom/base/nsJSEnvironment.h
@@ -81,13 +81,13 @@ public:
                                   nsAString *aRetValue,
                                   bool* aIsUndefined);
   virtual nsresult EvaluateStringWithValue(const nsAString& aScript,
-                                     void *aScopeObject,
-                                     nsIPrincipal *aPrincipal,
-                                     const char *aURL,
-                                     PRUint32 aLineNo,
-                                     PRUint32 aVersion,
-                                     void* aRetValue,
-                                     bool* aIsUndefined);
+                                           JSObject* aScopeObject,
+                                           nsIPrincipal* aPrincipal,
+                                           const char* aURL,
+                                           PRUint32 aLineNo,
+                                           PRUint32 aVersion,
+                                           void* aRetValue,
+                                           bool* aIsUndefined);
 
   virtual nsresult CompileScript(const PRUnichar* aText,
                                  PRInt32 aTextLength,
diff --git a/dom/plugins/base/nsNPAPIPlugin.cpp b/dom/plugins/base/nsNPAPIPlugin.cpp
index 8f0e4bbd6ebc..aa7f0625bc47 100644
--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -1646,6 +1646,8 @@ _evaluate(NPP npp, NPObject* npobj, NPString *script, NPVariant *result)
   }
 
   obj = JS_ObjectToInnerObject(cx, obj);
+  NS_ABORT_IF_FALSE(obj,
+    "JS_ObjectToInnerObject should never return null with non-null input.");
 
   // Root obj and the rval (below).
   jsval vec[] = { OBJECT_TO_JSVAL(obj), JSVAL_NULL };