diff --git a/content/xbl/src/nsXBLDocumentInfo.cpp b/content/xbl/src/nsXBLDocumentInfo.cpp
index f7a1fc2bbc0..d72c731a50a 100644
--- a/content/xbl/src/nsXBLDocumentInfo.cpp
+++ b/content/xbl/src/nsXBLDocumentInfo.cpp
@@ -78,6 +78,8 @@ public:
 
   void UnmarkScriptContext();
 
+  static JSClass gSharedGlobalClass;
+
 protected:
   virtual ~nsXBLDocGlobalObject();
 
@@ -87,7 +89,6 @@ protected:
   JSObject *mJSObject;
 
   nsXBLDocumentInfo* mGlobalObjectOwner; // weak reference
-  static JSClass gSharedGlobalClass;
 };
 
 bool
@@ -713,3 +714,13 @@ nsXBLDocumentInfo::GetScriptGlobalObject()
 
   return mGlobalObject;
 }
+
+#ifdef DEBUG
+void
+AssertInCompilationScope()
+{
+  AutoJSContext cx;
+  MOZ_ASSERT(JS_GetClass(JS::CurrentGlobalOrNull(cx)) ==
+             &nsXBLDocGlobalObject::gSharedGlobalClass);
+}
+#endif
diff --git a/content/xbl/src/nsXBLDocumentInfo.h b/content/xbl/src/nsXBLDocumentInfo.h
index 1f3507bff83..b5257501436 100644
--- a/content/xbl/src/nsXBLDocumentInfo.h
+++ b/content/xbl/src/nsXBLDocumentInfo.h
@@ -70,4 +70,10 @@ private:
   nsRefPtr<nsXBLDocGlobalObject> mGlobalObject;
 };
 
+#ifdef DEBUG
+void AssertInCompilationScope();
+#else
+inline void AssertInCompilationScope() {}
+#endif
+
 #endif