diff --git a/tests/extmod/time_ms_us.py b/tests/extmod/time_ms_us.py
index 31f07d31ba..4d0287da31 100644
--- a/tests/extmod/time_ms_us.py
+++ b/tests/extmod/time_ms_us.py
@@ -9,3 +9,6 @@ utime.sleep_ms(1)
 utime.sleep_us(1)
 print(utime.ticks_diff(utime.ticks_ms(), utime.ticks_ms()) <= 1)
 print(utime.ticks_diff(utime.ticks_us(), utime.ticks_us()) <= 500)
+
+# ticks_cpu may not be implemented, at least make sure it doesn't decrease
+print(utime.ticks_diff(utime.ticks_cpu(), utime.ticks_cpu()) >= 0)
diff --git a/tests/extmod/time_ms_us.py.exp b/tests/extmod/time_ms_us.py.exp
index dbde422651..b8ca7e7ef0 100644
--- a/tests/extmod/time_ms_us.py.exp
+++ b/tests/extmod/time_ms_us.py.exp
@@ -1,2 +1,3 @@
 True
 True
+True