--- a/browser/components/newtab/NewTabWebChannel.jsm
+++ b/browser/components/newtab/NewTabWebChannel.jsm
@@ -140,16 +140,20 @@ NewTabWebChannelImpl.prototype = {
 
     return false;
   },
 
   /*
    * Obtains all known browser refs
    */
   _getBrowserRefs() {
+    // Some code may try to emit messages after teardown.
+    if (!this._browsers) {
+      return [];
+    }
     let refs = [];
     for (let bRef of this._browsers) {
       /*
        * even though we hold a weak ref to browser, it seems that browser
        * objects aren't gc'd immediately after a tab closes. They stick around
        * in memory, but thankfully they don't have a documentURI in that case
        */
       let browser = bRef.get();