diff --git a/src/osmo_gsm_tester/obj/powersupply_sispm.py b/src/osmo_gsm_tester/obj/powersupply_sispm.py
index 0b1ad07..4fec83e 100644
--- a/src/osmo_gsm_tester/obj/powersupply_sispm.py
+++ b/src/osmo_gsm_tester/obj/powersupply_sispm.py
@@ -48,7 +48,7 @@
             except USBError as e:
                     if e.errno == 16 or e.errno==110:
                         self.log('skip usb error, retry', repr(e))
-                        MainLoop.sleep(self, 0.1)
+                        MainLoop.sleep(0.1)
                         continue
                     raise e