diff --git a/reference/json/functions/json-last-error.xml b/reference/json/functions/json-last-error.xml
index a72b68738f49..ead9a9fb2ae4 100644
--- a/reference/json/functions/json-last-error.xml
+++ b/reference/json/functions/json-last-error.xml
@@ -100,6 +100,11 @@
       <entry>Malformed UTF-16 characters, possibly incorrectly encoded</entry>
       <entry></entry>
      </row>
+     <row>
+      <entry><constant>JSON_ERROR_NON_BACKED_ENUM</constant></entry>
+      <entry>Value contains a non-backed enum which cannot be serialized. Available as of PHP 8.1.0.</entry>
+      <entry></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>