diff --git a/fs/bcachefs/alloc_background.c b/fs/bcachefs/alloc_background.c
index 6e161f8ffe8d..09ff41cac5f8 100644
--- a/fs/bcachefs/alloc_background.c
+++ b/fs/bcachefs/alloc_background.c
@@ -314,6 +314,10 @@ int bch2_alloc_v4_validate(struct bch_fs *c, struct bkey_s_c k,
 		break;
 	case BCH_DATA_stripe:
 		break;
+	default:
+		bkey_fsck_err_on(true, c, alloc_key_data_type_bad,
+				 "unknown data type %u", a.data_type);
+		break;
 	}
 fsck_err:
 	return ret;