diff --git a/ext/js/dom/document-util.js b/ext/js/dom/document-util.js
index 393ef294..8284ffa5 100644
--- a/ext/js/dom/document-util.js
+++ b/ext/js/dom/document-util.js
@@ -578,7 +578,7 @@ class DocumentUtil {
                     startContinerPre = startContainer;
                 }
 
-                previousStyles = new Map();
+                if (previousStyles === null) { previousStyles = new Map(); }
                 i = this._disableTransparentElement(elements, i, previousStyles);
                 if (i < 0) {
                     return null;