diff --git a/man5/tzfile.5 b/man5/tzfile.5
index 115cdc126..452265cdb 100644
--- a/man5/tzfile.5
+++ b/man5/tzfile.5
@@ -178,7 +178,7 @@ that is one hour east of UT.
 .SS Version 3 format
 For version-3-format timezone files, the POSIX-TZ-style string may
 use two minor extensions to the POSIX TZ format, as described in
-.IR newtzset (3).
+.BR newtzset (3).
 First, the hours part of its transition times may be signed and range from
 \-167 through 167 instead of the POSIX-required unsigned values
 from 0 through 24.