diff --git a/hosts.go b/hosts.go
index 8357754..87bef5e 100644
--- a/hosts.go
+++ b/hosts.go
@@ -145,7 +145,7 @@ func (f *FileHosts) isDomain(domain string) bool {
 	if f.isIP(domain) {
 		return false
 	}
-	match, _ := regexp.MatchString("^[a-zA-Z0-9][a-zA-Z0-9-]", domain)
+	match, _ := regexp.MatchString(`^([a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,6}$`, domain)
 	return match
 }