use macro for /usr/local/plan9
diff --git a/man/man1/db.1 b/man/man1/db.1
index b802100..fafa719 100644
--- a/man/man1/db.1
+++ b/man/man1/db.1
@@ -949,7 +949,7 @@
 .SH "SEE ALSO"
 .IR acid (1)
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/db
+.B \*9/src/cmd/db
 .SH DIAGNOSTICS
 Exit status is 0, unless the last command failed or
 returned non-zero status.