diff --git a/reference/mbstring/functions/mb-strlen.xml b/reference/mbstring/functions/mb-strlen.xml
index 45ffabd45f0b..91fcf1a587af 100644
--- a/reference/mbstring/functions/mb-strlen.xml
+++ b/reference/mbstring/functions/mb-strlen.xml
@@ -70,6 +70,14 @@
     </thead>
     <tbody>
      &mbstring.changelog.encoding-nullable;
+     <row>
+      <entry>8.0.0</entry>
+      <entry>
+       Passing an invalid encoding now throws a
+       <exceptionname>ValueError</exceptionname>. Previously, &false; was
+       returned.
+      </entry>
+     </row>
     </tbody>
    </tgroup>
   </informaltable>