diff --git a/css/selectors/heading.json b/css/selectors/heading.json
index 0bc76012921155..ac859c87e9cb10 100644
--- a/css/selectors/heading.json
+++ b/css/selectors/heading.json
@@ -4,6 +4,7 @@
       "heading": {
         "__compat": {
           "description": "`:heading`",
+          "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/:heading",
           "spec_url": "https://drafts.csswg.org/selectors-5/#headings",
           "support": {
             "chrome": {
diff --git a/css/selectors/headingfunction.json b/css/selectors/headingfunction.json
index 79d759b6a581ed..cc304ea62c1dea 100644
--- a/css/selectors/headingfunction.json
+++ b/css/selectors/headingfunction.json
@@ -4,6 +4,7 @@
       "headingfunction": {
         "__compat": {
           "description": "`:heading()`",
+          "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/:heading",
           "spec_url": "https://drafts.csswg.org/selectors-5/#headings",
           "support": {
             "chrome": {