diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index c9f9f3ded9e1a6f7772362b1d0e4a518b3fe4d4f..a7dc1e266c989de11bdc6ca06fa7f5ff20b04293 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1980,6 +1980,9 @@ int drm_mode_set_config_internal(struct drm_mode_set *set)
 
 	ret = crtc->funcs->set_config(set);
 	if (ret == 0) {
+		/* crtc->fb must be updated by ->set_config, enforces this. */
+		WARN_ON(fb != crtc->fb);
+
 		if (old_fb)
 			drm_framebuffer_unreference(old_fb);
 		if (fb)