diff --git a/reference/filesystem/functions/mkdir.xml b/reference/filesystem/functions/mkdir.xml
index e0dcea6e9c..c6300e31d6 100644
--- a/reference/filesystem/functions/mkdir.xml
+++ b/reference/filesystem/functions/mkdir.xml
@@ -16,7 +16,7 @@
    <methodparam choice="opt"><type>resource</type><parameter>context</parameter></methodparam>
   </methodsynopsis>
   <para>
-   Attempts to create the directory specified by pathname.
+   Attempts to create the directory specified by pathname. The directory must not already exist, and the relevant permissions must permit this. An E_WARNING level error will be generated on failure.
   </para>
  </refsect1>