diff --git a/src/osmo_gsm_tester/obj/powersupply.py b/src/osmo_gsm_tester/obj/powersupply.py
index bc7c0e3..7715a46 100644
--- a/src/osmo_gsm_tester/obj/powersupply.py
+++ b/src/osmo_gsm_tester/obj/powersupply.py
@@ -47,7 +47,7 @@
     def power_cycle(self, sleep=0):
         """Turns off the device, waits N.N seconds, then turn on the device."""
         self.power_set(False)
-        MainLoop.sleep(self, sleep)
+        MainLoop.sleep(sleep)
         self.power_set(True)
 
 def get_instance_by_type(pwsupply_type, pwsupply_opt):