diff --git a/reference/image/constants.xml b/reference/image/constants.xml
index f76b25af95..81693281fb 100644
--- a/reference/image/constants.xml
+++ b/reference/image/constants.xml
@@ -153,6 +153,18 @@
     </simpara>
    </listitem>
   </varlistentry>
+  <varlistentry xml:id="constant.img-webp">
+   <term>
+    <constant>IMG_WEBP</constant>
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     Used as a return value by <function>imagetypes</function>. Available as of
+     PHP 5.6.25 and PHP 7.0.10, respectively.
+    </simpara>
+   </listitem>
+  </varlistentry>
   <varlistentry xml:id="constant.img-color-tiled">
    <term>
     <constant>IMG_COLOR_TILED</constant> 
diff --git a/reference/image/functions/imagetypes.xml b/reference/image/functions/imagetypes.xml
index 19a26427bc..986ff5f6ff 100644
--- a/reference/image/functions/imagetypes.xml
+++ b/reference/image/functions/imagetypes.xml
@@ -22,7 +22,7 @@
    version of GD linked into PHP.  The following bits are returned, 
    <constant>IMG_GIF</constant> | <constant>IMG_JPG</constant> |
    <constant>IMG_PNG</constant> | <constant>IMG_WBMP</constant> | 
-   <constant>IMG_XPM</constant>.
+   <constant>IMG_XPM</constant> | <constant>IMG_WEBP</constant>.
   </para>
  </refsect1>
  <refsect1 role="examples">
@@ -42,6 +42,39 @@ if (imagetypes() & IMG_PNG) {
    </example>
   </para>
  </refsect1>
+
+<refsect1 role="changelog">
+  &reftitle.changelog;
+  <para>
+   <informaltable>
+    <tgroup cols="2">
+     <thead>
+      <row>
+       <entry>&Version;</entry>
+       <entry>&Description;</entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry>5.6.25, 7.0.10</entry>
+       <entry>
+        <constant>IMG_WEBP</constant> added.
+       </entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </informaltable>
+  </para>
+ </refsect1>
+
+ <refsect1 role="seealso">
+  &reftitle.seealso;
+  <para>
+   <simplelist>
+    <member><function>gd_info</function></member>
+   </simplelist>
+  </para>
+ </refsect1>
 </refentry>
 
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