gistfile1.txt

diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index 88b9944..8f7dfaf 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -710,6 +710,12 @@ def _emit_update_statements(base_mapper, uowtransaction,
                 for state, state_dict, params, mapper, \
                         connection, value_params, has_all_defaults, \
                         has_all_pks in records:
+
+                    msg = "Instance does not contain a non-NULL version value"
+                    if mapper.version_id_col is not None and \
+                        mapper.version_id_col.key not in params:
+                            raise orm_exc.FlushError(msg)
+
                     c = cached_connections[connection].\
                         execute(statement, params)