diff --git a/addons/web_editor/static/src/js/backend/convert_inline.js b/addons/web_editor/static/src/js/backend/convert_inline.js
index 707a673b97a..323ab5f23ee 100644
--- a/addons/web_editor/static/src/js/backend/convert_inline.js
+++ b/addons/web_editor/static/src/js/backend/convert_inline.js
@@ -336,8 +336,11 @@ function classToStyle($editable, cssRules) {
  *                                   specificity: number;}>
  */
 function toInline($editable, cssRules) {
+    const doc = $editable[0].ownerDocument;
+    cssRules = cssRules || doc._rulesCache;
     if (!cssRules) {
-        cssRules = getCSSRules($editable[0].ownerDocument);
+        cssRules = getCSSRules(doc);
+        doc._rulesCache = cssRules;
     }
 
     // Fix outlook image rendering bug (this change will be kept in both