diff --git a/cloud/apigw/main.go b/cloud/apigw/main.go
index d560c0c..9c0ebff 100644
--- a/cloud/apigw/main.go
+++ b/cloud/apigw/main.go
@@ -4,6 +4,8 @@
 	"context"
 	"flag"
 
+	"k8s.io/klog/v2"
+
 	"source.monogon.dev/cloud/apigw/server"
 )
 
@@ -11,6 +13,9 @@
 	s := &server.Server{}
 	s.Config.RegisterFlags()
 	flag.Parse()
+	if flag.NArg() > 0 {
+		klog.Exitf("unexpected positional arguments: %v", flag.Args())
+	}
 
 	ctx, ctxC := context.WithCancel(context.Background())
 	// TODO: context cancel on interrupt.