diff --git a/reference/var/functions/is-object.xml b/reference/var/functions/is-object.xml
index 346ae56ab1..0910185446 100644
--- a/reference/var/functions/is-object.xml
+++ b/reference/var/functions/is-object.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.4 $ -->
+<!-- $Revision: 1.5 $ -->
   <refentry id="function.is-object">
    <refnamediv>
     <refname>is_object</refname>
@@ -37,6 +37,16 @@
      &false; otherwise.
     </para>
    </refsect1>
+   <refsect1 role="notes">
+    &reftitle.notes;
+    <note>
+     <para>
+      This function will return &false; if used on an unserialized object
+      where the class definition is not present (even though
+      <function>gettype</function> returns <type>object</type>).
+     </para>
+    </note>
+   </refsect1>
    <refsect1 role="seealso">
     &reftitle.seealso;
     <para>