diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 931517133b..deb6779640 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -6963,11 +6963,14 @@ current:
 			else if (!(mc->mc_flags & C_SUB))
 				memcpy(olddata.mv_data, data->mv_data, data->mv_size);
 			else {
+				if (key->mv_size != NODEKSZ(leaf))
+					goto new_ksize;
 				memcpy(NODEKEY(leaf), key->mv_data, key->mv_size);
 				goto fix_parent;
 			}
 			return MDB_SUCCESS;
 		}
+new_ksize:
 		mdb_node_del(mc, 0);
 	}