diff --git a/usr.sbin/fdformat/Makefile b/usr.sbin/fdformat/Makefile
index 1a49c289b63..5325b6a1853 100644
--- a/usr.sbin/fdformat/Makefile
+++ b/usr.sbin/fdformat/Makefile
@@ -4,6 +4,6 @@ PROG    = fdformat
 # the -I's seem to be confusing, but necessery this way
 # (so the right <unistd.h> will be found in /usr/include, and the
 # "../i386/isa/ic/nec765.h" included from fdreg.h is accessible, too)
-CFLAGS+= -Wall -I/sys
+CFLAGS+= -Wall -I${DESTDIR}/sys
 
 .include <bsd.prog.mk>