use macro for /usr/local/plan9
diff --git a/man/man3/fmtinstall.3 b/man/man3/fmtinstall.3
index 8a437f1..d279bc8 100644
--- a/man/man3/fmtinstall.3
+++ b/man/man3/fmtinstall.3
@@ -362,7 +362,7 @@
 }
 .EE
 .SH SOURCE
-.B /usr/local/plan9/src/lib9/fmt
+.B \*9/src/lib9/fmt
 .SH SEE ALSO
 .IR print (3),
 .IR utf (7),