diff --git a/spinedb_api/helpers.py b/spinedb_api/helpers.py
index 2ee03567..339db057 100644
--- a/spinedb_api/helpers.py
+++ b/spinedb_api/helpers.py
@@ -49,7 +49,6 @@
     true,
 )
 from sqlalchemy.dialects.mysql import DOUBLE, TINYINT
-from sqlalchemy.engine import Connection
 from sqlalchemy.exc import DatabaseError, IntegrityError
 from sqlalchemy.ext.automap import generate_relationship
 from sqlalchemy.ext.compiler import compiles