diff --git a/reference/misc/functions/sleep.xml b/reference/misc/functions/sleep.xml
index fed67609e0..cc9f945b2e 100644
--- a/reference/misc/functions/sleep.xml
+++ b/reference/misc/functions/sleep.xml
@@ -37,9 +37,12 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   Returns zero on success, or &false; on errors. If the call was interrupted
-   by a signal, <function>sleep</function> returns the number of seconds left
-   to sleep.
+   On Windows, <function>sleep</function> always returns &null;.
+  </para>
+  <para>
+   On other platforms, <function>sleep</function> returns zero on success, or
+   &false; on errors. If the call was interrupted by a signal,
+   <function>sleep</function> returns the number of seconds left to sleep.
   </para>
  </refsect1>