Use dict

src/documents/migrations/1064_workflowaction_assign_custom_fields_values.py

@@ -18,7 +18,7 @@ class Migration(migrations.Migration):
                 help_text="Optional values to assign to the custom fields.",
                 null=True,
                 verbose_name="custom field values",
-                default={},
+                default=dict,
             ),
         ),
     ]

src/documents/models.py

@@ -1278,7 +1278,7 @@ class WorkflowAction(models.Model):
         help_text=_(
             "Optional values to assign to the custom fields.",
         ),
-        default={},
+        default=dict,
     )
 
     remove_tags = models.ManyToManyField(