diff --git a/control/fixed_duty.py b/control/fixed_duty.py
index e3c53ff..6040030 100644
--- a/control/fixed_duty.py
+++ b/control/fixed_duty.py
@@ -9,9 +9,9 @@ class FixedDutyCycle(controllers.Controller):
         self.set_duty(kwargs.pop('duty_perc'))
         operator = kwargs.pop('operator', '<')
         functions = {
-            '<': lambda (a, b): a < b,
-            '>': lambda (a, b): a > b,
-            '==': lambda (a, b): a == b,
+            '<': lambda a, b: a < b,
+            '>': lambda a, b: a > b,
+            '==': lambda a, b: a == b,
         }
         self.operator = functions[operator]
         super().__init__(*args, **kwargs)