--- a/dom/browser-element/BrowserElementChildPreload.js
+++ b/dom/browser-element/BrowserElementChildPreload.js
@@ -321,17 +321,19 @@ BrowserElementChild.prototype = {
     if (innerWindowID !== this._tryGetInnerWindowID(win)) {
       throw Components.Exception("Modal state aborted by navigation",
                                  Cr.NS_ERROR_NOT_AVAILABLE);
     }
 
     let returnValue = win.modalReturnValue;
     delete win.modalReturnValue;
 
-    utils.leaveModalStateWithWindow(modalStateWin);
+    if (!this._shuttingDown) {
+      utils.leaveModalStateWithWindow(modalStateWin);
+    }
 
     debug("Leaving modal state (outerID=" + outerWindowID + ", " +
                                "innerID=" + innerWindowID + ")");
     return returnValue;
   },
 
   _recvStopWaiting: function(msg) {
     let outerID = msg.json.windowID.outer;