diff --git a/browser/components/loop/standalone/content/js/standaloneMozLoop.js b/browser/components/loop/standalone/content/js/standaloneMozLoop.js
index 01986e4531a5..cc77c65ba2d4 100644
--- a/browser/components/loop/standalone/content/js/standaloneMozLoop.js
+++ b/browser/components/loop/standalone/content/js/standaloneMozLoop.js
@@ -109,16 +109,18 @@ loop.StandaloneMozLoop = (function(mozL10n) {
     /**
      * Internal function to actually perform a post to a room.
      *
-     * @param {String} roomToken The rom token.
+     * @param {String} roomToken    The room token.
      * @param {String} sessionToken The sessionToken for the room if known
-     * @param {Object} roomData The data to send with the request
+     * @param {Object} roomData     The data to send with the request
      * @param {Array} expectedProps The expected properties we should receive from the
      *                              server
+     * @param {Boolean} async       Set to true for an async request, false for sync.
      * @param {Function} callback The callback for when the request completes. The
      *                            first parameter is non-null on error, the second parameter
      *                            is the response data.
      */
-    _postToRoom: function(roomToken, sessionToken, roomData, expectedProps, callback) {
+    _postToRoom: function(roomToken, sessionToken, roomData, expectedProps,
+                          async, callback) {
       var req = $.ajax({
         url:         this._baseServerUrl + "/rooms/" + roomToken,
         method:      "POST",
@@ -129,19 +131,19 @@ loop.StandaloneMozLoop = (function(mozL10n) {
           if (sessionToken) {
             xhr.setRequestHeader("Authorization", "Basic " + btoa(sessionToken));
           }
-        }
+        },
+        async: async,
+        success: function(responseData) {
+          console.log("done");
+          try {
+            callback(null, validate(responseData, expectedProps));
+          } catch (err) {
+            console.error("Error requesting call info", err.message);
+            callback(err);
+          }
+        }.bind(this),
+        error: failureHandler.bind(this, callback)
       });
-
-      req.done(function(responseData) {
-        try {
-          callback(null, validate(responseData, expectedProps));
-        } catch (err) {
-          console.error("Error requesting call info", err.message);
-          callback(err);
-        }
-      }.bind(this));
-
-      req.fail(failureHandler.bind(this, callback));
     },
 
     /**
@@ -172,7 +174,7 @@ loop.StandaloneMozLoop = (function(mozL10n) {
         sessionId: String,
         sessionToken: String,
         expires: Number
-      }, callbackWrapper.bind(this));
+      }, true, callbackWrapper.bind(this));
     },
 
     /**
@@ -191,7 +193,7 @@ loop.StandaloneMozLoop = (function(mozL10n) {
         sessionToken: sessionToken
       }, {
         expires: Number
-      }, callback);
+      }, true, callback);
     },
 
     /**
@@ -214,10 +216,11 @@ loop.StandaloneMozLoop = (function(mozL10n) {
         };
       }
 
+      // We do this as a synchronous request in case this is closing the window.
       this._postToRoom(roomToken, sessionToken, {
         action: "leave",
         sessionToken: sessionToken
-      }, null, callback);
+      }, null, false, callback);
     },
 
     // Dummy functions to reflect those in the desktop mozLoop.rooms that we
diff --git a/browser/components/loop/test/standalone/standaloneMozLoop_test.js b/browser/components/loop/test/standalone/standaloneMozLoop_test.js
index 70688a07c190..9faa067d45b9 100644
--- a/browser/components/loop/test/standalone/standaloneMozLoop_test.js
+++ b/browser/components/loop/test/standalone/standaloneMozLoop_test.js
@@ -213,6 +213,7 @@ describe("loop.StandaloneMozLoop", function() {
       mozLoop.rooms.leave("fakeToken", "fakeSessionToken", callback);
 
       expect(requests).to.have.length.of(1);
+      expect(requests[0].async).eql(false);
       expect(requests[0].url).eql(fakeBaseServerUrl + "/rooms/fakeToken");
       expect(requests[0].method).eql("POST");
       expect(requests[0].requestHeaders.Authorization)