diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 1b3e0ff..ef87861 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -185,6 +185,9 @@
 	if (!file_priv->is_master)
 		return -EINVAL;
 
+	if (!file_priv->minor->master)
+		return -EINVAL;
+
 	mutex_lock(&dev->struct_mutex);
 	drm_master_put(&file_priv->minor->master);
 	file_priv->is_master = 0;