diff --git a/ports/raspberrypi/bindings/rp2pio/StateMachine.c b/ports/raspberrypi/bindings/rp2pio/StateMachine.c
index f8ced08177..be87a47ec5 100644
--- a/ports/raspberrypi/bindings/rp2pio/StateMachine.c
+++ b/ports/raspberrypi/bindings/rp2pio/StateMachine.c
@@ -97,7 +97,7 @@
 //|         """Construct a StateMachine object on the given pins with the given program.
 //|
 //|         :param ReadableBuffer program: the program to run with the state machine
-//|         :param int frequency: the target clock frequency of the state machine. Actual may be less.
+//|         :param int frequency: the target clock frequency of the state machine. Actual may be less. Use 0 for system clock speed.
 //|         :param ReadableBuffer init: a program to run once at start up. This is run after program
 //|              is started so instructions may be intermingled
 //|         :param ~microcontroller.Pin first_out_pin: the first pin to use with the OUT instruction