diff --git a/widget/MouseEvents.h b/widget/MouseEvents.h
index 7ad7d82cd688..ea714704df53 100644
--- a/widget/MouseEvents.h
+++ b/widget/MouseEvents.h
@@ -383,7 +383,9 @@ class WidgetDragEvent : public WidgetMouseEvent {
 
  protected:
   WidgetDragEvent()
-      : mUserCancelled(false), mDefaultPreventedOnContent(false) {}
+      : mUserCancelled(false),
+        mDefaultPreventedOnContent(false),
+        mInHTMLEditorEventListener(false) {}
 
  public:
   virtual WidgetDragEvent* AsDragEvent() override { return this; }
@@ -425,6 +427,8 @@ class WidgetDragEvent : public WidgetMouseEvent {
     // XXX mUserCancelled isn't copied, is this intentionally?
     mUserCancelled = false;
     mDefaultPreventedOnContent = aEvent.mDefaultPreventedOnContent;
+    // XXX mInHTMLEditorEventListener isn't copied, is this intentionally?
+    mInHTMLEditorEventListener = false;
   }
 
   /**
diff --git a/widget/nsGUIEventIPC.h b/widget/nsGUIEventIPC.h
index a3d7aaf1b6c6..8ba46829357f 100644
--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -270,13 +270,15 @@ struct ParamTraits<mozilla::WidgetDragEvent> {
     WriteParam(aWriter, static_cast<const mozilla::WidgetMouseEvent&>(aParam));
     WriteParam(aWriter, aParam.mUserCancelled);
     WriteParam(aWriter, aParam.mDefaultPreventedOnContent);
+    WriteParam(aWriter, aParam.mInHTMLEditorEventListener);
   }
 
   static bool Read(MessageReader* aReader, paramType* aResult) {
     bool rv =
         ReadParam(aReader, static_cast<mozilla::WidgetMouseEvent*>(aResult)) &&
         ReadParam(aReader, &aResult->mUserCancelled) &&
-        ReadParam(aReader, &aResult->mDefaultPreventedOnContent);
+        ReadParam(aReader, &aResult->mDefaultPreventedOnContent) &&
+        ReadParam(aReader, &aResult->mInHTMLEditorEventListener);
     return rv;
   }
 };