diff --git a/src/content/compatibility-dates/allow-custom-ports.md b/src/content/compatibility-dates/allow-custom-ports.md
index d230cfc550de7a..3d71bc660bf3c4 100644
--- a/src/content/compatibility-dates/allow-custom-ports.md
+++ b/src/content/compatibility-dates/allow-custom-ports.md
@@ -25,3 +25,4 @@ const response = await fetch("https://example.com:8000");
 With allow_custom_ports the above example would fetch `https://example.com:8000` rather than
 `https://example.com:443`.
 
+Note that creating a WebSocket client with a call to `new WebSocket(url)` will also obey this flag.