diff --git a/platform/firefox/vapi-background-ext.js b/platform/firefox/vapi-background-ext.js
index acc65da32..5d3ff8c5d 100644
--- a/platform/firefox/vapi-background-ext.js
+++ b/platform/firefox/vapi-background-ext.js
@@ -26,7 +26,12 @@ import {
 
 /******************************************************************************/
 
-const dnsAPI = browser.dns;
+const dnsAPI = browser.dns || {
+    resolve() {
+        return Promise.resolve();
+    }
+};
+
 const isPromise = o => o instanceof Promise;
 const isResolvedObject = o => o instanceof Object &&
     o instanceof Promise === false;