diff --git a/reference/filter/constants.xml b/reference/filter/constants.xml
index 2ff05f6bd932..35864c8f6cf9 100644
--- a/reference/filter/constants.xml
+++ b/reference/filter/constants.xml
@@ -1215,12 +1215,6 @@ NULL
 ]]>
      </screen>
     </example>
-    <warning>
-     <simpara>
-      This filter cannot be used with any other filter flags, e.g.
-      <constant>FILTER_NULL_ON_FAILURE</constant>.
-     </simpara>
-    </warning>
    </listitem>
   </varlistentry>
  </variablelist>