diff --git a/language/oop5/interfaces.xml b/language/oop5/interfaces.xml
index 5f5a0770d9..d4757e4466 100644
--- a/language/oop5/interfaces.xml
+++ b/language/oop5/interfaces.xml
@@ -36,6 +36,13 @@
      operator.
     </para>
    </note>
+   <note>
+    <para>
+     The class implementing the interface must use the exact same method
+     signatures as are defined in the interface. Not doing so will result in a
+     fatal error.
+     </para>
+    </note>
   </sect2>
   <sect2 xml:id="language.oop5.interfaces.constants">
    <title><literal>Constants</literal></title>
@@ -202,10 +209,13 @@ class b implements a
 ]]>
      </programlisting>
    </example>
-   <simpara>
-     See also the <link linkend="language.operators.type">instanceof</link>
+   <para>
+     An interface, together with type-hinting, provides a good way to make sure
+     that a particular object contains particular methods. See
+     <link linkend="language.operators.type">instanceof</link> and
+     <link linkend="language.oop5.typehinting">type hinting</link>.
      operator.
-   </simpara>
+   </para>
   </sect2>
 
  </sect1>