diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
index 94c2e94..3d3690f 100644
--- a/hw/usb/dev-mtp.c
+++ b/hw/usb/dev-mtp.c
@@ -965,12 +965,16 @@
 static MTPData *usb_mtp_get_partial_object(MTPState *s, MTPControl *c,
                                            MTPObject *o)
 {
-    MTPData *d = usb_mtp_data_alloc(c);
+    MTPData *d;
     off_t offset;
 
+    if (c->argc <= 2) {
+        return NULL;
+    }
     trace_usb_mtp_op_get_partial_object(s->dev.addr, o->handle, o->path,
                                         c->argv[1], c->argv[2]);
 
+    d = usb_mtp_data_alloc(c);
     d->fd = open(o->path, O_RDONLY);
     if (d->fd == -1) {
         usb_mtp_data_free(d);