diff --git a/artiq/test/coredevice/test_spi.py b/artiq/test/coredevice/test_spi.py
index 436f720d9..53b1a3ec0 100644
--- a/artiq/test/coredevice/test_spi.py
+++ b/artiq/test/coredevice/test_spi.py
@@ -9,6 +9,7 @@ class Collision(EnvExperiment):
 
     @kernel
     def run(self):
+        self.core.break_realtime()
         t = now_mu()
         self.spi0.set_config_mu()
         at_mu(t)
@@ -23,6 +24,7 @@ class Busy(EnvExperiment):
 
     @kernel
     def run(self):
+        self.core.break_realtime()
         t = now_mu()
         self.spi0.set_config_mu()
         at_mu(t + self.spi0.ref_period_mu)