diff --git a/system/vl.c b/system/vl.c
index 92fc29c193..bdd2f6ecf6 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -1674,7 +1674,7 @@ static MachineClass *select_machine(QDict *qdict, Error **errp)
         machine_class = find_machine(machine_type, machines);
         qdict_del(qdict, "type");
         if (!machine_class) {
-            error_setg(errp, "unsupported machine type");
+            error_setg(errp, "unsupported machine type: \"%s\"", optarg);
         }
     } else {
         machine_class = find_default_machine(machines);