diff --git a/dom/websocket/WebSocket.cpp b/dom/websocket/WebSocket.cpp
index a92ba2d5c7e0..305a6c9a7ca7 100644
--- a/dom/websocket/WebSocket.cpp
+++ b/dom/websocket/WebSocket.cpp
@@ -225,8 +225,6 @@ class WebSocketImpl final : public nsIInterfaceRequestor,
 
  private:
   ~WebSocketImpl() {
-    MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread() == mIsMainThread);
-
     // If we threw during Init we never called disconnect
     if (!mDisconnectingOrDisconnected) {
       Disconnect();
@@ -234,9 +232,42 @@ class WebSocketImpl final : public nsIInterfaceRequestor,
   }
 };
 
-NS_IMPL_ISUPPORTS(WebSocketImpl, nsIInterfaceRequestor, nsIWebSocketListener,
-                  nsIObserver, nsISupportsWeakReference, nsIRequest,
-                  nsIEventTarget)
+NS_IMPL_ADDREF(WebSocketImpl)
+NS_IMPL_QUERY_INTERFACE(WebSocketImpl, nsIInterfaceRequestor,
+                        nsIWebSocketListener, nsIObserver,
+                        nsISupportsWeakReference, nsIRequest, nsIEventTarget)
+
+NS_IMETHODIMP_(MozExternalRefCountType) WebSocketImpl::Release(void) {
+  MOZ_ASSERT(int32_t(mRefCnt) > 0, "dup release");
+
+  if (!mRefCnt.isThreadSafe) {
+    NS_ASSERT_OWNINGTHREAD(WebSocketImpl);
+  }
+
+  nsrefcnt count = mRefCnt - 1;
+  // If WebSocketImpl::Disconnect is not called, the last release of
+  // WebSocketImpl should be on the right thread.
+  if (count == 0 && !IsTargetThread() && !mDisconnectingOrDisconnected) {
+    DebugOnly<nsresult> rv = Dispatch(NewNonOwningRunnableMethod(
+        "dom::WebSocketImpl::Release", this, &WebSocketImpl::Release));
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+    return count;
+  }
+
+  count = --mRefCnt;
+  NS_LOG_RELEASE(this, count, "WebSocketImpl");
+
+  if (count == 0) {
+    if (!mRefCnt.isThreadSafe) {
+      NS_ASSERT_OWNINGTHREAD(WebSocketImpl);
+    }
+
+    mRefCnt = 1; /* stabilize */
+    delete (this);
+    return 0;
+  }
+  return count;
+}
 
 class CallDispatchConnectionCloseEvents final : public CancelableRunnable {
  public:
@@ -541,12 +572,12 @@ class DisconnectInternalRunnable final : public WorkerMainThreadRunnable {
 }  // namespace
 
 void WebSocketImpl::Disconnect() {
-  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread() == mIsMainThread);
-
   if (mDisconnectingOrDisconnected) {
     return;
   }
 
+  AssertIsOnTargetThread();
+
   // DontKeepAliveAnyMore() and DisconnectInternal() can release the object. So
   // hold a reference to this until the end of the method.
   RefPtr<WebSocketImpl> kungfuDeathGrip = this;