diff --git a/main.go b/main.go
index eaa4b08..497efc9 100644
--- a/main.go
+++ b/main.go
@@ -33,7 +33,7 @@ import (
 )
 
 const (
-	version = "0.6"
+	version = "0.6.1"
 )
 
 var (
@@ -84,6 +84,10 @@ func main() {
 	}
 
 	args := os.Args
+	if len(os.Args) < 2 {
+		pflag.Usage()
+		os.Exit(1)
+	}
 	filename := args[len(args)-1]
 
 	var f *os.File