diff --git a/doc/api/tls.md b/doc/api/tls.md
index fe8bfa27ef6ca2..1f2b8906b5f4b2 100644
--- a/doc/api/tls.md
+++ b/doc/api/tls.md
@@ -891,7 +891,7 @@ changes:
     first byte is the length of the next protocol name. Passing an array is
     usually much simpler, e.g. `['hello', 'world']`.
   * `servername`: {string} Server name for the SNI (Server Name Indication) TLS
-    extension.
+    extension. It must be a host name, and not an IP address.
   * `checkServerIdentity(servername, cert)` {Function} A callback function
     to be used (instead of the builtin `tls.checkServerIdentity()` function)
     when checking the server's hostname (or the provided `servername` when