diff --git a/doc/api/url.md b/doc/api/url.md
index 27b3b69e4447d2..0dde9e625603c5 100644
--- a/doc/api/url.md
+++ b/doc/api/url.md
@@ -942,6 +942,9 @@ invalid domain, the empty string is returned.
 
 It performs the inverse operation to [`url.domainToUnicode()`][].
 
+This feature is only available if the `node` executable was compiled with
+[ICU][] enabled. If not, the domain names are passed through unchanged.
+
 ```mjs
 import url from 'url';
 
@@ -979,6 +982,9 @@ domain, the empty string is returned.
 
 It performs the inverse operation to [`url.domainToASCII()`][].
 
+This feature is only available if the `node` executable was compiled with
+[ICU][] enabled. If not, the domain names are passed through unchanged.
+
 ```mjs
 import url from 'url';