diff --git a/Makefile b/Makefile
index 6d6d8f4..696e080 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ PSBOOK = psbook
 PSTOPS = pstops
 PSNUP = psnup
 PS2PDF = ps2pdf
-SED = sed # do not use in-place editing for compatibility between different sed utilities
+SED = sed # do not use in-place editing for compatibility between different sed versions 
 RM = rm
 MKDIR = mkdir
 CD = cd