diff --git a/artiq/coredevice/ttl.py b/artiq/coredevice/ttl.py
index 91c8c5531..28248a820 100644
--- a/artiq/coredevice/ttl.py
+++ b/artiq/coredevice/ttl.py
@@ -37,6 +37,10 @@ class TTLOut:
         # in RTIO cycles
         self.o_previous_timestamp = int(0, width=64)
 
+    @kernel
+    def output(self):
+        pass
+
     @kernel
     def set_o(self, o):
         ttl_set_o(now_mu(), self.channel, o)
diff --git a/artiq/test/coredevice/test_rtio.py b/artiq/test/coredevice/test_rtio.py
index ff50bf51c..50958392f 100644
--- a/artiq/test/coredevice/test_rtio.py
+++ b/artiq/test/coredevice/test_rtio.py
@@ -8,6 +8,7 @@ from math import sqrt
 from artiq.experiment import *
 from artiq.test.hardware_testbench import ExperimentCase
 
+
 artiq_low_latency = os.getenv("ARTIQ_LOW_LATENCY")