diff --git a/reference/classobj/functions/is-subclass-of.xml b/reference/classobj/functions/is-subclass-of.xml
index f8789f81fa..018acf5ab0 100644
--- a/reference/classobj/functions/is-subclass-of.xml
+++ b/reference/classobj/functions/is-subclass-of.xml
@@ -26,7 +26,7 @@
      <term><parameter>object</parameter></term>
      <listitem>
       <para>
-       A class name or an object instance
+       A class name or an object instance. No error is generated if the class does not exist.
       </para>
      </listitem>
     </varlistentry>
@@ -54,7 +54,7 @@
   &reftitle.returnvalues;
   <para>
    This function returns &true; if the object <parameter>object</parameter>,
-   belongs to a class which is a subclass of 
+   belongs to a class which is a subclass of
    <parameter>class_name</parameter>, &false; otherwise.
   </para>
  </refsect1>
@@ -80,7 +80,7 @@
        <entry>5.3.7</entry>
        <entry>
         Added support for <parameter>class_name</parameter> to work with
-        interfaces 
+        interfaces
        </entry>
       </row>
       <row>