diff --git a/authentic2_idp_oauth2/admin.py b/authentic2_idp_oauth2/admin.py
index 883e3e3..179c1d1 100644
--- a/authentic2_idp_oauth2/admin.py
+++ b/authentic2_idp_oauth2/admin.py
@@ -12,14 +12,18 @@ class WebServiceAdmin(admin.ModelAdmin):
     prepopulated_fields = {'slug': ('name',)}
 
 class AttributeReleaselineForm(forms.ModelForm):
-    class Meta:
-        def choices(ctx):
-            return [('', _('None'))] + get_attribute_names(ctx)
+    def __init__(self, *args, **kwargs):
+        super(AttributeReleaselineForm, self).__init__(*args, **kwargs)
+        choices = self.choices({'user': None, 'request': None})
+        self.fields['attribute_name'].choices = choices
+        self.fields['attribute_name'].widget = forms.Select(choices=choices)
 
+    @to_iter
+    def choices(self, ctx):
+        return [('', _('None'))] + get_attribute_names(ctx)
+
+    class Meta:
         model = models.AttributeRelease
-        widgets = {
-                'attribute_name': forms.Select(choices=to_iter(choices)({'user': None, 'request': None}))
-        }
 
 class AttributeReleaseInline(admin.TabularInline):
     model = models.AttributeRelease