diff --git a/man/man3/matrix.3 b/man/man3/matrix.3
index 87ba34c..7291725 100644
--- a/man/man3/matrix.3
+++ b/man/man3/matrix.3
@@ -345,6 +345,6 @@
 .I z
 coordinates.
 .SH SOURCE
-.B /usr/local/plan9/src/libgeometry/matrix.c
+.B \*9/src/libgeometry/matrix.c
 .SH "SEE ALSO
 .IR arith3 (3)