diff --git a/language/oop5/magic.xml b/language/oop5/magic.xml
index adaf93c420..a5a7aaa4c0 100644
--- a/language/oop5/magic.xml
+++ b/language/oop5/magic.xml
@@ -288,6 +288,19 @@ object(A)#2 (2) {
 ]]>
     </screen>
    </example>
+   <note>
+    <simpara>
+     When exporting an object, <function>var_export</function> does not check
+     whether <link linkend="object.set-state">__set_state()</link> is
+     implemented by the object's class, so re-importing such objects will fail,
+     if __set_state() is not implemented. Particularly, this affects some
+     internal classes.
+    </simpara>
+    <simpara>
+     It is the responsibility of the programmer to verify that only objects will
+     be re-imported, whose class implements __set_state().
+    </simpara>
+   </note>
   </sect2>
 
   <sect2 xml:id="language.oop5.magic.debuginfo">