diff --git a/scripts/metricsgen/metricsdiff/metricsdiff.go b/scripts/metricsgen/metricsdiff/metricsdiff.go
index 043390309..04519013e 100644
--- a/scripts/metricsgen/metricsdiff/metricsdiff.go
+++ b/scripts/metricsgen/metricsdiff/metricsdiff.go
@@ -48,15 +48,15 @@ type LabelDiff struct {
 func main() {
 	flag.Parse()
 	if flag.NArg() != 2 {
-		log.Fatalf("Usage is %s <path1> <path2>, got %d arguments",
+		log.Fatalf("Usage is '%s <path1> <path2>', got %d arguments",
 			filepath.Base(os.Args[0]), flag.NArg())
 	}
-	fa, err := os.Open(os.Args[1])
+	fa, err := os.Open(flag.Arg(0))
 	if err != nil {
 		log.Fatalf("Open: %v", err)
 	}
 	defer fa.Close()
-	fb, err := os.Open(os.Args[2])
+	fb, err := os.Open(flag.Arg(1))
 	if err != nil {
 		log.Fatalf("Open: %v", err)
 	}