diff --git a/reference/uopz/setup.xml b/reference/uopz/setup.xml
index adacf998c5..befbbf4b6c 100644
--- a/reference/uopz/setup.xml
+++ b/reference/uopz/setup.xml
@@ -109,6 +109,14 @@
     </varlistentry>
    </variablelist>
   </para>
+
+  <note>
+   <simpara>
+    When running with OPcache enabled, it may be necessary to disable all
+    <link linkend="ini.opcache.optimization-level">OPcache optimizations</link>
+    (<code>opcache.optimization_level=0</code>).
+   </simpara>
+  </note>
  </section>
 
  <section xml:id="uopz.resources">