diff --git a/dom/base/WebSocket.cpp b/dom/base/WebSocket.cpp
index af4b7858b..1b9ca3d00 100644
--- a/dom/base/WebSocket.cpp
+++ b/dom/base/WebSocket.cpp
@@ -960,6 +960,11 @@ WebSocket::Constructor(const GlobalObject& aGlobal,
                        const nsAString& aUrl,
                        ErrorResult& aRv)
 {
+  if (!PrefEnabled()) {
+    aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
+    return nullptr;
+  }
+
   Sequence<nsString> protocols;
   return WebSocket::ConstructorCommon(aGlobal, aUrl, protocols, nullptr,
                                       EmptyCString(), aRv);
@@ -1483,6 +1488,11 @@ WebSocketImpl::Init(JSContext* aCx,
   AssertIsOnMainThread();
   MOZ_ASSERT(aPrincipal);
 
+  if (!WebSocket::PrefEnabled()) {
+    aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
+    return;
+  }
+
   mService = WebSocketEventService::GetOrCreate();
 
   // We need to keep the implementation alive in case the init disconnects it
@@ -2054,6 +2064,11 @@ WebSocket::CreateAndDispatchCloseEvent(bool aWasClean,
   return DispatchDOMEvent(nullptr, event, nullptr, nullptr);
 }
 
+bool
+WebSocket::PrefEnabled()
+{
+  return Preferences::GetBool("network.websocket.enabled", true);
+}
 nsresult
 WebSocketImpl::ParseURL(const nsAString& aURL)
 {
diff --git a/dom/base/WebSocket.h b/dom/base/WebSocket.h
index f5fd170de..351a48ae6 100644
--- a/dom/base/WebSocket.h
+++ b/dom/base/WebSocket.h
@@ -63,7 +63,7 @@ public:
 public: // static helpers:
 
   // Determine if preferences allow WebSocket
-  static bool PrefEnabled(JSContext* aCx = nullptr, JSObject* aGlobal = nullptr);
+  static bool PrefEnabled();
 
 public: // WebIDL interface:
 
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 7b8bc21a0..38d95e1c9 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1646,6 +1646,9 @@ pref("network.sts.max_time_for_events_between_two_polls", 100);
 pref("network.sts.max_time_for_pr_close_during_shutdown", 5000);
 // </http>
 
+// <ws>: WebSocket
+pref("network.websocket.enabled", true);
+
 // 2147483647 == PR_INT32_MAX == ~2 GB
 pref("network.websocket.max-message-size", 2147483647);