diff --git a/gnu/usr.bin/groff/tmac/mdoc.local b/gnu/usr.bin/groff/tmac/mdoc.local
index db9abb70fdea..0472637f64aa 100644
--- a/gnu/usr.bin/groff/tmac/mdoc.local
+++ b/gnu/usr.bin/groff/tmac/mdoc.local
@@ -54,6 +54,7 @@
 .ds doc-operating-system FreeBSD\~5.0
 .
 .\" FreeBSD releases not found in doc-common
+.ds doc-operating-system-FreeBSD-4.6.1    4.6.1
 .ds doc-operating-system-FreeBSD-4.7    4.7
 .ds doc-operating-system-FreeBSD-4.8    4.8
 .