diff --git a/cloud/bmaas/server/cmd/main.go b/cloud/bmaas/server/cmd/main.go
index 2d04841..dd99205 100644
--- a/cloud/bmaas/server/cmd/main.go
+++ b/cloud/bmaas/server/cmd/main.go
@@ -4,6 +4,8 @@
 	"context"
 	"flag"
 
+	"k8s.io/klog/v2"
+
 	"source.monogon.dev/cloud/bmaas/server"
 	clicontext "source.monogon.dev/metropolis/cli/pkg/context"
 )
@@ -12,6 +14,9 @@
 	s := &server.Server{}
 	s.Config.RegisterFlags()
 	flag.Parse()
+	if flag.NArg() > 0 {
+		klog.Exitf("unexpected positional arguments: %v", flag.Args())
+	}
 
 	ctx := clicontext.WithInterrupt(context.Background())
 	s.Start(ctx)