diff --git a/dom/wifi/WifiProxyService.cpp b/dom/wifi/WifiProxyService.cpp
index 63e36d90cef..1a310a5eaf8 100644
--- a/dom/wifi/WifiProxyService.cpp
+++ b/dom/wifi/WifiProxyService.cpp
@@ -248,6 +248,10 @@ WifiProxyService::SendCommand(JS::Handle<JS::Value> aOptions,
     return NS_ERROR_FAILURE;
   }
 
+  if (!mControlThread) {
+    return NS_ERROR_FAILURE;
+  }
+
   // Dispatch the command to the control thread.
   CommandOptions commandOptions(options);
   nsCOMPtr<nsIRunnable> runnable = new ControlRunnable(commandOptions, aInterface);
@@ -293,8 +297,10 @@ WifiProxyService::DispatchWifiResult(const WifiResultOptions& aOptions, const ns
     return;
   }
 
-  // Call the listener with a JS value.
-  mListener->OnCommand(val, aInterface);
+  if (mListener) {
+    // Call the listener with a JS value.
+    mListener->OnCommand(val, aInterface);
+  }
 }
 
 void
diff --git a/dom/wifi/WifiWorker.js b/dom/wifi/WifiWorker.js
index 4abf19794e8..5e7128c52ba 100644
--- a/dom/wifi/WifiWorker.js
+++ b/dom/wifi/WifiWorker.js
@@ -1432,6 +1432,14 @@ var WifiManager = (function() {
                               ? wifiCommand.getConnectionInfoICS
                               : wifiCommand.getConnectionInfoGB;
 
+  manager.ensureSupplicantDetached = aCallback => {
+    if (!manager.enabled) {
+      aCallback();
+      return;
+    }
+    wifiCommand.closeSupplicantConnection(aCallback);
+  };
+
   manager.isHandShakeState = function(state) {
     switch (state) {
       case "AUTHENTICATING":
@@ -3820,10 +3828,14 @@ WifiWorker.prototype = {
       break;
 
     case "xpcom-shutdown":
-      let wifiService = Cc["@mozilla.org/wifi/service;1"].getService(Ci.nsIWifiProxyService);
-      wifiService.shutdown();
-      let wifiCertService = Cc["@mozilla.org/wifi/certservice;1"].getService(Ci.nsIWifiCertService);
-      wifiCertService.shutdown();
+      // Ensure the supplicant is detached from B2G to avoid XPCOM shutdown
+      // blocks forever.
+      WifiManager.ensureSupplicantDetached(() => {
+        let wifiService = Cc["@mozilla.org/wifi/service;1"].getService(Ci.nsIWifiProxyService);
+        wifiService.shutdown();
+        let wifiCertService = Cc["@mozilla.org/wifi/certservice;1"].getService(Ci.nsIWifiCertService);
+        wifiCertService.shutdown();
+      });
       break;
     }
   },