--- a/devtools/server/actors/inspector.js
+++ b/devtools/server/actors/inspector.js
@@ -2342,16 +2342,23 @@ var WalkerActor = protocol.ActorClassWit
       type: "inlineTextChild",
       target: parentActor.actorID,
       inlineTextChild:
         inlineTextChild ? inlineTextChild.form() : undefined
     });
   },
 
   onFrameLoad: function ({ window, isTopLevel }) {
+    let { readyState } = window.document;
+    if (readyState != "interactive" && readyState != "complete") {
+      window.addEventListener("DOMContentLoaded",
+        this.onFrameLoad.bind(this, { window, isTopLevel }),
+        { once: true });
+      return;
+    }
     if (isTopLevel) {
       // If we initialize the inspector while the document is loading,
       // we may already have a root document set in the constructor.
       if (this.rootDoc && !Cu.isDeadWrapper(this.rootDoc) &&
           this.rootDoc.defaultView) {
         this.onFrameUnload({ window: this.rootDoc.defaultView });
       }
       this.rootDoc = window.document;