diff --git a/main.go b/main.go
index 6120451..1ba39a3 100644
--- a/main.go
+++ b/main.go
@@ -43,7 +43,7 @@ func main() {
 
 	dir, valid := os.LookupEnv("STATE_DIRECTORY")
 	if !valid {
-		log.Fatal("RUNTIME_DIRECTORY must be set")
+		log.Fatal("STATE_DIRECTORY must be set")
 	}
 	s := &tsnet.Server{
 		Hostname: hostname,