it was introduced with #20566 as a result of merge Signed-off-by: Alexander Morozov <lk4d4@docker.com>
@@ -242,6 +242,7 @@ func Parse(cmd *flag.FlagSet, args []string) (*container.Config, *container.Host
entrypoint = strslice.StrSlice{*flEntrypoint}
}
// Validate if the given hostname is RFC 1123 (https://tools.ietf.org/html/rfc1123) compliant.
+ hostname := *flHostname
if hostname != "" {
matched, _ := regexp.MatchString("^(([[:alnum:]]|[[:alnum:]][[:alnum:]\\-]*[[:alnum:]])\\.)*([[:alnum:]]|[[:alnum:]][[:alnum:]\\-]*[[:alnum:]])$", hostname)
if !matched {