man: Add missing doc-operating-system-NetBSD string variable Fixes: commit 99320b9168ffb0112def1a712e8d59441d1b46d9.
diff --git a/man/vis.3bsd b/man/vis.3bsd
index 00d9ebe..7895af4 100644
--- a/man/vis.3bsd
+++ b/man/vis.3bsd
@@ -529,6 +529,7 @@ The destination buffer size is not large enough to perform the conversion.
.%O "RFC 2045"
.Re
.Sh HISTORY
+.ds doc-operating-system-NetBSD-7.0 7.0
The
.Fn vis ,
.Fn strvis ,