diff --git a/cmd/apidiff/main.go b/cmd/apidiff/main.go
index aeaf1a7..d29c90f 100644
--- a/cmd/apidiff/main.go
+++ b/cmd/apidiff/main.go
@@ -40,6 +40,7 @@
 	if *exportDataOutfile != "" {
 		if len(flag.Args()) != 1 {
 			flag.Usage()
+			os.Exit(2)
 		}
 		pkg := mustLoadPackage(flag.Arg(0))
 		if err := writeExportData(pkg, *exportDataOutfile); err != nil {
@@ -48,6 +49,7 @@
 	} else {
 		if len(flag.Args()) != 2 {
 			flag.Usage()
+			os.Exit(2)
 		}
 		oldpkg := mustLoadOrRead(flag.Arg(0))
 		newpkg := mustLoadOrRead(flag.Arg(1))