diff --git a/apps/search_indexes/signals.py b/apps/search_indexes/signals.py
index 77660a2c..3da50fb8 100644
--- a/apps/search_indexes/signals.py
+++ b/apps/search_indexes/signals.py
@@ -38,7 +38,7 @@ def update_document(sender, **kwargs):
                 for establishment in establishments:
                     registry.update(establishment)
         if model_name == 'establishmentsubtype':
-            if instance(instance, establishment_models.EstablishmentSubType):
+            if isinstance(instance, establishment_models.EstablishmentSubType):
                 establishments = Establishment.objects.filter(
                     establishment_subtypes=instance)
                 for establishment in establishments: