diff --git a/docs/library/utime.rst b/docs/library/utime.rst
index 47d93c4c5a..e678321f6a 100644
--- a/docs/library/utime.rst
+++ b/docs/library/utime.rst
@@ -36,7 +36,9 @@ Functions
     .. function:: sleep(seconds)
     
        Sleep for the given number of seconds.  Seconds can be a floating-point number to
-       sleep for a fractional number of seconds.
+       sleep for a fractional number of seconds. Note that other MicroPython ports may
+       not accept floating-point argument, for compatibility with them use ``sleep_ms()``
+       and ``sleep_us()`` functions.
 
 .. only:: port_wipy