--- a/js/src/xpconnect/src/nsXPConnect.cpp
+++ b/js/src/xpconnect/src/nsXPConnect.cpp
@@ -2503,17 +2503,18 @@ nsXPConnect::Push(JSContext * cx)
         bool runningJS = false;
         for (PRUint32 i = 0; i < stack->Length(); ++i) {
             JSContext *cx = (*stack)[i].cx;
             if (cx && cx->regs) {
                 runningJS = true;
                 break;
             }
         }
-        if (!runningJS)
+        /* Turning debugging off is immediate even if JS is running */
+        if (!runningJS || !gDesiredDebugMode)
             CheckForDebugMode(mRuntime->GetJSRuntime());
     }
 
     return data->GetJSContextStack()->Push(cx);
 }
 
 /* attribute JSContext SafeJSContext; */
 NS_IMETHODIMP
@@ -2772,16 +2773,18 @@ nsXPConnect::Base64Decode(JSContext *cx,
     *out = STRING_TO_JSVAL(str);
     return JS_TRUE;
 }
 
 NS_IMETHODIMP
 nsXPConnect::SetDebugModeWhenPossible(PRBool mode)
 {
     gDesiredDebugMode = mode;
+    if (!mode)
+        CheckForDebugMode(mRuntime->GetJSRuntime());
     return NS_OK;
 }
 
 /* These are here to be callable from a debugger */
 JS_BEGIN_EXTERN_C
 JS_EXPORT_API(void) DumpJSStack()
 {
     nsresult rv;