diff --git a/toolkit/devtools/server/actors/webbrowser.js b/toolkit/devtools/server/actors/webbrowser.js
index 70924e4c82d6..c35073744a5e 100644
--- a/toolkit/devtools/server/actors/webbrowser.js
+++ b/toolkit/devtools/server/actors/webbrowser.js
@@ -285,7 +285,8 @@ BrowserTabList.prototype._getBrowsers = function*() {
 };
 
 BrowserTabList.prototype._getChildren = function(aWindow) {
-  return aWindow.gBrowser ? aWindow.gBrowser.browsers : [];
+  let children = aWindow.gBrowser ? aWindow.gBrowser.browsers : [];
+  return children ? children : [];
 };
 
 BrowserTabList.prototype._isRemoteBrowser = function(browser) {