From a76f308efbbb2a7836b81dec2c6341f7150dfc94 Mon Sep 17 00:00:00 2001
From: Peter Tillema <petertillema@solcon.nl>
Date: Wed, 27 May 2020 15:26:51 +0200
Subject: [PATCH] Use True value for isnull field

---
 advanced_filters/forms.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/advanced_filters/forms.py b/advanced_filters/forms.py
index 726622b..f4e6269 100644
--- a/advanced_filters/forms.py
+++ b/advanced_filters/forms.py
@@ -92,7 +92,7 @@ def _build_query_dict(self, formdata=None):
             formdata = self.cleaned_data
         key = "{field}__{operator}".format(**formdata)
         if formdata['operator'] == "isnull":
-            return {key: None}
+            return {key: True}
         elif formdata['operator'] == "istrue":
             return {formdata['field']: True}
         elif formdata['operator'] == "isfalse":