diff --git a/artiq/sim/devices.py b/artiq/sim/devices.py
index fc258ed48..7704bb1a6 100644
--- a/artiq/sim/devices.py
+++ b/artiq/sim/devices.py
@@ -1,6 +1,6 @@
 from random import Random
 
-from artiq.language.core import kernel, sequential, delay_mu
+from artiq.language.core import kernel, sequential, at_mu, delay_mu
 from artiq.sim import time