diff --git a/language/oop5/abstract.xml b/language/oop5/abstract.xml
index d5c336951d..e06ca85549 100644
--- a/language/oop5/abstract.xml
+++ b/language/oop5/abstract.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.3 $ -->
+<!-- $Revision: 1.4 $ -->
  <sect1 id="language.oop5.abstract">
   <title>Object Abstraction</title>
 
@@ -11,6 +11,13 @@
    define the implementation.
   </para>
 
+  <para>
+   The class that implements the abstract method must define with the same
+   <link linkend="oop5.visibility">visibillity</link> or weaker.  If the
+   abstract method is defined as protected, the function implenetation must be
+   defined as either protected or public.
+  </para>
+
   <example>
    <title>Abstract class example</title>
     <programlisting role="php">
@@ -59,7 +66,6 @@ $class2->print();
     Old code that has no user-defined classes or functions named
     'abstract' should run without modifications.
    </para>
-
  </sect1>
  
 <!-- Keep this comment at the end of the file