diff --git a/ports/raspberrypi/common-hal/pulseio/PulseIn.c b/ports/raspberrypi/common-hal/pulseio/PulseIn.c
index b9052f3c60..fb05876b95 100644
--- a/ports/raspberrypi/common-hal/pulseio/PulseIn.c
+++ b/ports/raspberrypi/common-hal/pulseio/PulseIn.c
@@ -1,4 +1,4 @@
-/*
+b/*
  * This file is part of the MicroPython project, http://micropython.org/
  *
  * The MIT License (MIT)