diff --git a/reference/filesystem/functions/realpath.xml b/reference/filesystem/functions/realpath.xml
index d354d2c278..793ad1cfa7 100644
--- a/reference/filesystem/functions/realpath.xml
+++ b/reference/filesystem/functions/realpath.xml
@@ -29,6 +29,12 @@
      <listitem>
       <para>
        The path being checked.
+       <note>
+        <para>
+         Whilst a path must be supplied, the value can be blank or &null;
+         In these cases, the value is interpreted as the current directory.
+        </para>
+       </note>
       </para>
      </listitem>
     </varlistentry>
@@ -75,6 +81,13 @@
         component did not exist.
        </entry>
       </row>
+      <row>
+       <entry>5.0.0</entry>
+       <entry>
+        Prior to this release, a blank or &null; <parameter>path</parameter> would
+        cause <function>realpath</function> to return the directory name of the script.
+       </entry>
+      </row>
      </tbody>
     </tgroup>
    </informaltable>