diff --git a/toolkit/components/jsdownloads/src/DownloadIntegration.jsm b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
index 34be122de83c..b0d08ef81092 100644
--- a/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
+++ b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
@@ -791,7 +791,13 @@ this.DownloadIntegration = {
 
     if (this.dontOpenFileAndFolder) {
       deferred.then((value) => { this._deferTestShowDir.resolve("success"); },
-                    (error) => { this._deferTestShowDir.reject(error); });
+                    (error) => {
+                      // Ensure that _deferTestShowDir has at least one consumer
+                      // for the error, otherwise the error will be reported as
+                      // uncaught.
+                      this._deferTestShowDir.promise.then(null, function() {});
+                      this._deferTestShowDir.reject(error);
+                    });
     }
 
     return deferred;