diff --git a/trytond/trytond/protocols/dispatcher.py b/trytond/trytond/protocols/dispatcher.py
index f5b0a5e20a..72c6eec5a9 100644
--- a/trytond/trytond/protocols/dispatcher.py
+++ b/trytond/trytond/protocols/dispatcher.py
@@ -212,11 +212,13 @@ def _dispatch(request, pool, *args, **kwargs):
                             for i in inst]
             except TransactionError as e:
                 transaction.rollback()
+                transaction.tasks.clear()
                 e.fix(transaction_extras)
                 continue
             except backend.DatabaseOperationalError:
                 if count < retry and not rpc.readonly:
                     transaction.rollback()
+                    transaction.tasks.clear()
                     count += 1
                     logger.debug("Retry: %i", count)
                     continue