diff --git a/addons/website_mail/static/src/js/website_email_designer.js b/addons/website_mail/static/src/js/website_email_designer.js
index b2ce7286281..4bc778c2130 100644
--- a/addons/website_mail/static/src/js/website_email_designer.js
+++ b/addons/website_mail/static/src/js/website_email_designer.js
@@ -240,7 +240,9 @@
                                 selectorText.indexOf(":after") === -1 &&
                                 selectorText.indexOf(":active") === -1 &&
                                 selectorText.indexOf(":link") === -1 &&
-                                selectorText.indexOf("::") === -1) {
+                                selectorText.indexOf("::") === -1 &&
+                                selectorText.indexOf("\"") === -1 &&
+                                selectorText.indexOf("'") === -1) {
                             var st = selectorText.split(/\s*,\s*/);
                             for (var k=0; k<st.length; k++) {
                                 rulesCache.push({