diff --git a/mistral/db/sqlalchemy/migration/alembic_migrations/versions/038_delete_delayed_calls_with_empty_key.py b/mistral/db/sqlalchemy/migration/alembic_migrations/versions/038_delete_delayed_calls_with_empty_key.py
new file mode 100644
index 000000000..8f5493fb6
--- /dev/null
+++ b/mistral/db/sqlalchemy/migration/alembic_migrations/versions/038_delete_delayed_calls_with_empty_key.py
@@ -0,0 +1,47 @@
+# Copyright 2020 Nokia Software.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Delete delayed calls with key=NULL.
+
+Revision ID: 038
+Revises: 037
+Create Date: 2020-7-13 13:20:00
+
+"""
+
+# revision identifiers, used by Alembic.
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.sql import table, column
+
+revision = '038'
+down_revision = '037'
+
+
+def upgrade():
+    # See https://bugs.launchpad.net/mistral/+bug/1861988.
+    # Due to this bug there may be redundant delayed calls in DB.
+    # We need to delete all rows where the "key" column is None.
+    session = sa.orm.Session(bind=op.get_bind())
+
+    delayed_calls = table('delayed_calls_v2', column('key'))
+
+    with session.begin(subtransactions=True):
+        session.execute(
+            delayed_calls.delete().where(delayed_calls.c.key==None)  # noqa
+        )
+
+    session.commit()