diff --git a/Makefile b/Makefile
index 3e7c0f3..8114cfc 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@ PREFIX ?= /usr/local
 
 MANDIR != [ $(PREFIX) = / ] && printf '/usr/share/man\n' \
 	|| printf '/share/man\n'
-SYSEXITS != </dev/null cpp -M -include sysexits.h - | tr ' ' '\n' \
+SYSEXITS != cpp -M -include sysexits.h /dev/null | tr ' ' '\n' \
 	| sed -n 's/sysexits\.h//p' || printf 'include\n'
 
 CC ?= cc