diff --git a/artiq/frontend/artiq_sinara_tester.py b/artiq/frontend/artiq_sinara_tester.py
index 81e7370f9..b6869b7d8 100755
--- a/artiq/frontend/artiq_sinara_tester.py
+++ b/artiq/frontend/artiq_sinara_tester.py
@@ -209,6 +209,7 @@ class SinaraTester(EnvExperiment):
             print("Testing TTL outputs: {}.".format(", ".join(name for name, dev in ttl_chunk)))
             self.test_ttl_out_chunk([dev for name, dev in ttl_chunk])
 
+    # NAC3TODO https://git.m-labs.hk/M-Labs/nac3/issues/101
     @kernel
     def test_ttl_in(self, ttl_out: TTLOut, ttl_in: TTLInOut) -> bool:
         n = 42