diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 7303bbd6..26cf99df 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -89,7 +89,7 @@ bool check_drm_features(struct wlr_drm_backend *drm) {
 }
 
 static bool add_plane(struct wlr_drm_backend *drm,
-		struct wlr_drm_crtc *crtc, drmModePlane *drm_plane,
+		struct wlr_drm_crtc *crtc, const drmModePlane *drm_plane,
 		uint32_t type, union wlr_drm_plane_props *props) {
 	assert(!(type == DRM_PLANE_TYPE_PRIMARY && crtc->primary));
 	assert(!(type == DRM_PLANE_TYPE_CURSOR && crtc->cursor));