diff --git a/django_dbml/management/commands/dbml.py b/django_dbml/management/commands/dbml.py
index 93710ee..31fa2c4 100644
--- a/django_dbml/management/commands/dbml.py
+++ b/django_dbml/management/commands/dbml.py
@@ -38,7 +38,10 @@ def get_field_notes(self, field):
 
             if name == "default":
                 if callable(value):
-                    value = "{}.{}()".format(inspect.getmodule(value).__name__, value.__name__)
+                    if inspect.getmodule(value):
+                        value = "{}.{}()".format(inspect.getmodule(value).__name__, value.__name__)
+                    else:
+                        value = "{}()".format(value.__name__)
                 elif isinstance(value, str):
                     value = "\"{}\"".format(value)
                 attributes.append('default:`{}`'.format(value))