diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 2d06f3b..513706d 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -4939,7 +4939,8 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 					rc = MDB_NOTFOUND;
 					mc->mc_ki[mc->mc_top]++;
 				} else {
-					rc = 0;
+					/* new key is <= last key */
+					rc = MDB_KEYEXIST;
 				}
 			}
 		} else {
@@ -6918,7 +6919,7 @@ mdb_put(MDB_txn *txn, MDB_dbi dbi,
 		return EINVAL;
 	}
 
-	if ((flags & (MDB_NOOVERWRITE|MDB_NODUPDATA|MDB_RESERVE|MDB_APPEND)) != flags)
+	if ((flags & (MDB_NOOVERWRITE|MDB_NODUPDATA|MDB_RESERVE|MDB_APPEND|MDB_APPENDDUP)) != flags)
 		return EINVAL;
 
 	mdb_cursor_init(&mc, txn, dbi, &mx);