diff --git a/argparse.go b/argparse.go
index 37a5da1..b1f2509 100644
--- a/argparse.go
+++ b/argparse.go
@@ -39,7 +39,7 @@ func New() *Parser {
 
 func (p *Parser) addArg(a *arg) error {
 	for _, v := range p.args {
-		if v.sname == a.sname || v.lname == a.lname {
+		if (a.sname != "" && v.sname == a.sname) || (a.lname != "" && v.lname == a.lname) {
 			return errors.New("option name dup")
 		}
 	}