diff --git a/build/media_source/plg_editors_tinymce/js/plugins/highlighter/source.es5.js b/build/media_source/plg_editors_tinymce/js/plugins/highlighter/source.es5.js
index b0139dc493eb3..a7522d3038c3c 100644
--- a/build/media_source/plg_editors_tinymce/js/plugins/highlighter/source.es5.js
+++ b/build/media_source/plg_editors_tinymce/js/plugins/highlighter/source.es5.js
@@ -272,7 +272,7 @@ document.addEventListener('keydown', (evt) => {
   // Without this, the background color outside of the codemirror wrapper element remains white.
   // [TMP] commented temporary, cause JS error: Uncaught TypeError: Cannot read property 'replace' of undefined
   if(CMsettings.config.theme) {
-    document.documentElement.className += CMsettings.config.theme.replace(/(^|\s)\s*/g, " cm-s-");
+    document.documentElement.className += CMsettings.config.theme.replace(/(^|\s)\s*/g, ' cm-s-');
   }
 
   window.onload = start;