diff --git a/app/flask-postgres/app/app.py b/app/flask-postgres/app/app.py
index 2538a28..b423edd 100644
--- a/app/flask-postgres/app/app.py
+++ b/app/flask-postgres/app/app.py
@@ -711,12 +711,14 @@ def useradmin_user_new():
                 new_user_id = cur.fetchone()[0]
 
                 if selected_groups:
+                    selected_group_ids = [int(gid) for gid in selected_groups]
+
                     cur.execute("""
                         SELECT id
                         FROM app_group
                         WHERE mandant_id = %s
-                          AND id = ANY(%s)
-                    """, (current_mandant_id, selected_groups))
+                        AND id = ANY(%s)
+                    """, (current_mandant_id, selected_group_ids))
                     valid_groups = cur.fetchall()
 
                     for row in valid_groups: