--- a/doc/ctmconv.1
+++ b/doc/ctmconv.1
@@ -24,7 +24,7 @@
 Scale the mesh by a scalar factor.
 .TP
 .B --upaxis arg
-Set up axis (X, Y, Z, -X, -Y, -Z). If != Z, the mesh will be flipped.
+Set up axis (X, Y, Z, \-X, \-Y, \-Z). If != Z, the mesh will be flipped.
 .TP
 .B --flip
 Flip triangle orientation.