--- a/sys/dev/drm/radeon/radeon_connectors.c
+++ b/sys/dev/drm/radeon/radeon_connectors.c
@@ -547,6 +547,8 @@
 			continue;
 
 		mode = drm_cvt_mode(dev, common_modes[i].w, common_modes[i].h, 60, false, false, false);
+		if (!mode)
+			continue;
 		drm_mode_probed_add(connector, mode);
 	}
 }
@@ -1146,6 +1148,8 @@
 	else {
 		/* only 800x600 is supported right now on pre-avivo chips */
 		tv_mode = drm_cvt_mode(dev, 800, 600, 60, false, false, false);
+		if (!tv_mode)
+			return 0;
 		tv_mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
 		drm_mode_probed_add(connector, tv_mode);
 	}