diff --git a/gnu/usr.bin/diff/Makefile b/gnu/usr.bin/diff/Makefile
index 23070eef97c9..c5c66dcce0ec 100644
--- a/gnu/usr.bin/diff/Makefile
+++ b/gnu/usr.bin/diff/Makefile
@@ -17,11 +17,10 @@ CFLAGS+=-funsigned-char
 
 CFLAGS+=-DHAVE_CONFIG_H
 CFLAGS+=-DPR_PROGRAM=\"/usr/bin/pr\"
-CFLAGS+=-D__USE_GNU
 CFLAGS+=-I${.CURDIR}/../../../contrib/diff
 CFLAGS+=-I${.CURDIR}/../../../contrib/diff/src
 CFLAGS+=-I${.CURDIR}/../../../contrib/diff/lib
-CFLAGS+=-I${.CURDIR}/../../../contrib/libgnuregex
+CFLAGS+=-I${DESTDIR}/usr/include/gnu
 
 SUBDIR+=doc
 
diff --git a/gnu/usr.bin/grep/Makefile b/gnu/usr.bin/grep/Makefile
index 8c3d77883e54..7d3b60769b8d 100644
--- a/gnu/usr.bin/grep/Makefile
+++ b/gnu/usr.bin/grep/Makefile
@@ -13,8 +13,7 @@ SRCS=	closeout.c dfa.c error.c exclude.c grep.c grepmat.c hard-locale.c \
 	isdir.c kwset.c obstack.c quotearg.c savedir.c search.c xmalloc.c \
 	xstrtoumax.c
 
-CFLAGS+=-I${.CURDIR} -I${.CURDIR}/../../../contrib/libgnuregex
-CFLAGS+=-DHAVE_CONFIG_H -D__USE_GNU
+CFLAGS+=-I${.CURDIR} -I${DESTDIR}/usr/include/gnu -DHAVE_CONFIG_H
 
 .if ${MK_BSD_GREP} != "yes"
 LINKS+=	${BINDIR}/grep ${BINDIR}/egrep \
diff --git a/usr.bin/grep/Makefile b/usr.bin/grep/Makefile
index 359954b13cfa..8b2fa0c49703 100644
--- a/usr.bin/grep/Makefile
+++ b/usr.bin/grep/Makefile
@@ -74,7 +74,7 @@ CFLAGS+= -DWITHOUT_BZIP2
 .endif
 
 .if !defined(WITHOUT_GNU_COMPAT)
-CFLAGS+= -I/usr/include/gnu
+CFLAGS+= -I${DESTDIR}/usr/include/gnu
 LDADD+=	-lgnuregex
 DPADD+=	${LIBGNUREGEX}
 .endif