diff --git a/reference/exec/functions/proc-open.xml b/reference/exec/functions/proc-open.xml
index a90bf4c285..eb1e09331f 100644
--- a/reference/exec/functions/proc-open.xml
+++ b/reference/exec/functions/proc-open.xml
@@ -134,10 +134,12 @@
          <literal>context</literal>: stream context used when opening files
          (created with <function>stream_context_create</function>)
         </member>
+        <!--  FIXME PHP_6 
         <member>
          <literal>binary_pipes</literal>: open pipes in binary mode, instead
          of using the usual <literal>stream_encoding</literal>
         </member>
+        -->
        </simplelist>
       </para>
      </listitem>