diff --git a/mellon/adapters.py b/mellon/adapters.py
index fa97c68..f23fe68 100644
--- a/mellon/adapters.py
+++ b/mellon/adapters.py
@@ -87,6 +87,9 @@ class DefaultAdapter(object):
                 log.warning('invalid reference in attribute mapping template %r: %s', tpl, e)
             else:
                 attribute_set = True
+                model_field = user._meta.get_field(field)
+                if hasattr(model_field, 'max_length'):
+                    value = value[:model_field.max_length]
                 setattr(user, field, value)
         if attribute_set:
             user.save()
diff --git a/tests/test_default_adapter.py b/tests/test_default_adapter.py
index e6a6252..5fc9b31 100644
--- a/tests/test_default_adapter.py
+++ b/tests/test_default_adapter.py
@@ -77,3 +77,16 @@ def test_provision(settings):
     adapter.provision(user, idp, local_saml_attributes)
     assert not user.email
     User.objects.all().delete()
+
+    local_saml_attributes = saml_attributes.copy()
+    settings.MELLON_ATTRIBUTE_MAPPING = {
+        'email': '{attributes[email][0]}',
+        'first_name': '{attributes[first_name][0]}',
+        'last_name': '{attributes[last_name][0]}',
+    }
+    local_saml_attributes['first_name'] = [('y' * 32)]
+    user = User(username='xx')
+    user.save()
+    adapter.provision(user, idp, local_saml_attributes)
+    assert user.first_name == 'y' * 30
+    User.objects.all().delete()