diff --git a/artiq/test/coredevice/test_rtio.py b/artiq/test/coredevice/test_rtio.py
index 881c16ae9..17caf7450 100644
--- a/artiq/test/coredevice/test_rtio.py
+++ b/artiq/test/coredevice/test_rtio.py
@@ -48,6 +48,7 @@ class Loopback(EnvExperiment):
     @kernel
     def run(self):
         self.loop_in.input()
+        self.loop_out.off()
         delay(1*us)
         with parallel:
             self.loop_in.gate_rising(2*us)