diff --git a/reference/mbstring/functions/mb-detect-encoding.xml b/reference/mbstring/functions/mb-detect-encoding.xml
index f3ca5c880f..80114d436e 100644
--- a/reference/mbstring/functions/mb-detect-encoding.xml
+++ b/reference/mbstring/functions/mb-detect-encoding.xml
@@ -62,7 +62,8 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   The detected character encoding.
+   The detected character encoding of &false; if the encoding cannot be
+   detected from the given string.
   </para>
  </refsect1>