diff --git a/django/db/models/functions/datetime.py b/django/db/models/functions/datetime.py
index 2c6d66d2e6..a8e1ca45c1 100644
--- a/django/db/models/functions/datetime.py
+++ b/django/db/models/functions/datetime.py
@@ -148,7 +148,6 @@ ExtractYear.register_lookup(YearLte)
 
 
 class TruncBase(TimezoneMixin, Transform):
-    arity = 1
     kind = None
     tzinfo = None