diff --git a/ext/js/dom/sandbox/css-style-applier.js b/ext/js/dom/sandbox/css-style-applier.js
index 6c45f13e..0f44df0a 100644
--- a/ext/js/dom/sandbox/css-style-applier.js
+++ b/ext/js/dom/sandbox/css-style-applier.js
@@ -53,8 +53,7 @@ class CssStyleApplier {
         this._styleDataUrl = styleDataUrl;
         this._styleData = [];
         this._cachedRules = new Map();
-        // eslint-disable-next-line no-control-regex
-        this._patternHtmlWhitespace = /[\t\r\n\x0C ]+/g;
+        this._patternHtmlWhitespace = /[\t\r\n\f ]+/g;
         this._patternClassNameCharacter = /[0-9a-zA-Z-_]/;
     }
 
diff --git a/ext/js/dom/simple-dom-parser.js b/ext/js/dom/simple-dom-parser.js
index bc327f5e..f5489d5e 100644
--- a/ext/js/dom/simple-dom-parser.js
+++ b/ext/js/dom/simple-dom-parser.js
@@ -22,8 +22,7 @@
 class SimpleDOMParser {
     constructor(content) {
         this._document = parse5.parse(content);
-        // eslint-disable-next-line no-control-regex
-        this._patternHtmlWhitespace = /[\t\r\n\x0C ]+/g;
+        this._patternHtmlWhitespace = /[\t\r\n\f ]+/g;
     }
 
     getElementById(id, root=null) {