--- a/browser/devtools/webide/content/webide.js
+++ b/browser/devtools/webide/content/webide.js
@@ -241,18 +241,21 @@ let UI = {
     this._busyOperationDescription = operationDescription;
     this.setupBusyTimeout();
     this.busy();
     promise.then(() => {
       this.cancelBusyTimeout();
       this.unbusy();
     }, (e) => {
       this.cancelBusyTimeout();
-      UI.reportError("error_operationFail", operationDescription);
-      console.error(e);
+      let operationCanceled = e && e.canceled;
+      if (!operationCanceled) {
+        UI.reportError("error_operationFail", operationDescription);
+        console.error(e);
+      }
       this.unbusy();
     });
     return promise;
   },
 
   reportError: function(l10nProperty, ...l10nArgs) {
     let text;
 

--- a/browser/devtools/webide/modules/app-manager.js
+++ b/browser/devtools/webide/modules/app-manager.js
@@ -332,17 +332,17 @@ exports.AppManager = AppManager = {
           deferred.reject();
         }
       }
       this.connection.on(Connection.Events.CONNECTED, onConnectedOrDisconnected);
       this.connection.on(Connection.Events.DISCONNECTED, onConnectedOrDisconnected);
       try {
         this.selectedRuntime.connect(this.connection).then(
           () => {},
-          () => {deferred.reject()});
+          deferred.reject.bind(deferred));
       } catch(e) {
         console.error(e);
         deferred.reject();
       }
     }, deferred.reject);
 
     return deferred.promise;
   },

--- a/browser/devtools/webide/modules/runtimes.js
+++ b/browser/devtools/webide/modules/runtimes.js
@@ -121,21 +121,23 @@ let gLocalRuntime = {
 
 let gRemoteRuntime = {
   connect: function(connection) {
     let win = Services.wm.getMostRecentWindow("devtools:webide");
     if (!win) {
       return promise.reject();
     }
     let ret = {value: connection.host + ":" + connection.port};
-    Services.prompt.prompt(win,
-                           Strings.GetStringFromName("remote_runtime_promptTitle"),
-                           Strings.GetStringFromName("remote_runtime_promptMessage"),
-                           ret, null, {});
+    let title = Strings.GetStringFromName("remote_runtime_promptTitle");
+    let message = Strings.GetStringFromName("remote_runtime_promptMessage");
+    let ok = Services.prompt.prompt(win, title, message, ret, null, {});
     let [host,port] = ret.value.split(":");
+    if (!ok) {
+      return promise.reject({canceled: true});
+    }
     if (!host || !port) {
       return promise.reject();
     }
     connection.host = host;
     connection.port = port;
     connection.connect();
     return promise.resolve();
   },