diff --git a/documentation/ref-manual/ref-classes.xml b/documentation/ref-manual/ref-classes.xml
index 979e7344b0..d65ac0b0bd 100644
--- a/documentation/ref-manual/ref-classes.xml
+++ b/documentation/ref-manual/ref-classes.xml
@@ -940,6 +940,31 @@
     </para>
 </section>
 
+<section id='ref-classes-image-types'>
+    <title><filename>image-types.bbclass</filename></title>
+
+    <para>
+        The image types (<filename>image-types</filename>) class defines all of
+        the standard image output types that you can enable through the
+        <link linkend='var-IMAGE_FSTYPES'><filename>IMAGE_FSTYPES</filename></link>
+        variable.
+        You can use this class as a reference on how to add support for custom
+        image output types.
+    </para>
+
+    <para>
+        By default, this class is enabled through the
+        <link linkend='var-IMAGE_CLASSES'><filename>IMAGE_CLASSES</filename></link>
+        variable in
+        <link linkend='ref-classes-image'><filename>image.bbclass</filename></link>.
+        If you define your own image types using a custom BitBake class and
+        then use <filename>IMAGE_CLASSES</filename> to enable it, the custom
+        class must either inherit <filename>image-types</filename> or
+        <filename>image-types</filename> must also appear in
+        <filename>IMAGE_CLASSES</filename>.
+    </para>
+</section>
+
 <section id='ref-classes-mime'>
     <title><filename>mime.bbclass</filename></title>