diff --git a/css/at-rules/container.json b/css/at-rules/container.json
index b2b20240371fb1..af29cb1ee4f8df 100644
--- a/css/at-rules/container.json
+++ b/css/at-rules/container.json
@@ -66,7 +66,8 @@
               "opera": "mirror",
               "opera_android": "mirror",
               "safari": {
-                "version_added": "18"
+                "version_added": "18",
+                "notes": "The document element cannot be a container. See <a href='https://webkit.org/b/271040'>bug 271040</a>."
               },
               "safari_ios": "mirror",
               "samsunginternet_android": "mirror",