diff --git a/reference/pgsql/functions/pg-field-num.xml b/reference/pgsql/functions/pg-field-num.xml
index 2d1ee6b71e..22ade3a0d2 100644
--- a/reference/pgsql/functions/pg-field-num.xml
+++ b/reference/pgsql/functions/pg-field-num.xml
@@ -41,6 +41,8 @@
       <listitem>
        <para>
         The name of the field.
+        The given name is treated like an identifier in an SQL command,
+        that is, it is downcased unless double-quoted.
        </para>
      </listitem>
     </varlistentry>