diff --git a/nixos/doc/manual/release-notes/rl-2009.xml b/nixos/doc/manual/release-notes/rl-2009.xml
index ff5b50132ee1..4122a1fb8e5b 100644
--- a/nixos/doc/manual/release-notes/rl-2009.xml
+++ b/nixos/doc/manual/release-notes/rl-2009.xml
@@ -594,8 +594,8 @@ systemd.services.nginx.serviceConfig.ReadWritePaths = [ "/var/www" ];
    <listitem>
      <para>
        The hostname (<literal>networking.hostName</literal>) must now be a valid
-       DNS label (see RFC 1035) and as such must not contain the domain part.
-       This means that the hostname must start with a letter, end with a letter
+       DNS label (see RFC 1035, RFC 1123) and as such must not contain the domain part.
+       This means that the hostname must start with a letter or digit, end with a letter
        or digit, and have as interior characters only letters, digits, and
        hyphen. The maximum length is 63 characters. Additionally it is
        recommended to only use lower-case characters.
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 9ff2326db1fe..b956f49c036c 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -381,13 +381,14 @@ in
       # syntax). Note: We also allow underscores for compatibility/legacy
       # reasons (as undocumented feature):
       type = types.strMatching
-        "^$|^[[:alpha:]]([[:alnum:]_-]{0,61}[[:alnum:]])?$";
+        "^$|^[[:alnum:]]([[:alnum:]_-]{0,61}[[:alnum:]])?$";
       description = ''
         The name of the machine. Leave it empty if you want to obtain it from a
         DHCP server (if using DHCP). The hostname must be a valid DNS label (see
-        RFC 1035 section 2.3.1: "Preferred name syntax") and as such must not
-        contain the domain part. This means that the hostname must start with a
-        letter, end with a letter or digit, and have as interior characters only
+        RFC 1035 section 2.3.1: "Preferred name syntax", RFC 1123 section 2.1:
+        "Host Names and Numbers") and as such must not contain the domain part.
+        This means that the hostname must start with a letter or digit,
+        end with a letter or digit, and have as interior characters only
         letters, digits, and hyphen. The maximum length is 63 characters.
         Additionally it is recommended to only use lower-case characters.
       '';