diff --git a/src/js/modules/webslides.js b/src/js/modules/webslides.js
index a47affd..2dd6267 100644
--- a/src/js/modules/webslides.js
+++ b/src/js/modules/webslides.js
@@ -428,13 +428,15 @@ export default class WebSlides {
       || document.mozFullScreen
       || document.msFullScreenElement;
 
-    if(!isFullscreen) {
+    if (!isFullscreen) {
+      /* istanbul ignore next hard to test prefixes */
       const requestFullscreen = el.requestFullscreen
           || el.webkitRequestFullScreen
           || el.mozRequestFullScreen
           || el.msRequestFullscreen;
       requestFullscreen.call(el);
     } else {
+      /* istanbul ignore next hard to test prefixes */
       const cancelFullscreen = document.exitFullScreen
         || document.webkitCancelFullScreen
         || document.mozCancelFullScreen
diff --git a/test/modules/webslides.test.js b/test/modules/webslides.test.js
index fdf0733..6412f3f 100644
--- a/test/modules/webslides.test.js
+++ b/test/modules/webslides.test.js
@@ -377,11 +377,14 @@ test('Fullscreen', () => {
   document.fullscreen = false;
   document.documentElement.requestFullscreen = jest.fn();
   document.exitFullScreen = jest.fn();
+
+  expect(document.documentElement.requestFullscreen).not.toHaveBeenCalled();
   webslides.fullscreen();
-  expect(document.documentElement.requestFullscreen.mock.calls.length).toBe(1);
+  expect(document.documentElement.requestFullscreen).toHaveBeenCalled();
   document.fullscreen = true;
+  expect(document.exitFullScreen).not.toHaveBeenCalled();
   webslides.fullscreen();
-  expect(document.exitFullScreen.mock.calls.length).toBe(1);
+  expect(document.exitFullScreen).toHaveBeenCalled();
 });
 
 test('Zoom', () => {