diff --git a/en_US.ISO8859-1/books/faq/book.sgml b/en_US.ISO8859-1/books/faq/book.sgml
index 3bb16946e1..ca7724aa90 100644
--- a/en_US.ISO8859-1/books/faq/book.sgml
+++ b/en_US.ISO8859-1/books/faq/book.sgml
@@ -3964,7 +3964,7 @@ kern.timecounter.hardware: TSC -&gt; i8254</screen>
               block for an extended period while holding a mutex.</para>
 
           <para>To catch such errors, assertions may be added to the kernel
-              that interact with the witness subsystem to emit a warning
+              that interact with the &man.witness.4; subsystem to emit a warning
               or fatal error (depending on the system configuration) when
               a potentially blocking call is made while holding a mutex.</para>