diff --git a/viewporter/viewporter-tests.ts b/viewporter/viewporter-tests.ts
index 35c8c2ae46..9ce0be298a 100644
--- a/viewporter/viewporter-tests.ts
+++ b/viewporter/viewporter-tests.ts
@@ -119,7 +119,7 @@ function test_swipey() {
         }).trigger(viewporter.ACTIVE ? 'viewportchange' : 'resize');
         $('canvas').bind(iOS ? 'touchstart' : 'mousedown', function (e) {
             e.preventDefault();
-            var touches = iOS ? e.originalEvent.changedTouches : [e.originalEvent];
+            var touches = iOS ? (<any>e.originalEvent).changedTouches : [e.originalEvent];
             var identifier;
             for (var i = 0; i < touches.length; i++) {
                 identifier = touches[i].identifier || 'mouse';
@@ -133,7 +133,7 @@ function test_swipey() {
         });
 
         $('canvas').bind(iOS ? 'touchmove' : 'mousemove', function (e) {
-            var touches = iOS ? e.originalEvent.changedTouches : [e.originalEvent];
+			var touches = iOS ? (<any>e.originalEvent).changedTouches : [e.originalEvent];
             var identifier;
             for (var i = 0; i < touches.length; i++) {
                 identifier = touches[i].identifier || 'mouse';
@@ -144,7 +144,7 @@ function test_swipey() {
         });
 
         $('canvas').bind(iOS ? 'touchend' : 'mouseup', function (e) {
-            var touches = iOS ? e.originalEvent.changedTouches : [e.originalEvent];
+			var touches = iOS ? (<any>e.originalEvent).changedTouches : [e.originalEvent];
             var identifier;
             for (var i = 0; i < touches.length; i++) {
                 identifier = touches[i].identifier || 'mouse';