diff --git a/Makefile.extra b/Makefile.extra
index e92ffec..53f15bb 100644
--- a/Makefile.extra
+++ b/Makefile.extra
@@ -1,6 +1,7 @@
 # -*- Makefile -*-
 # AUTOMAKE
 
+export AM_CPPFLAGS
 export AM_CFLAGS
 XA_SRCDIR = ${srcdir}
 XA_TOPSRCDIR = ${top_srcdir}
diff --git a/Makefile.iptrules.in b/Makefile.iptrules.in
index b6b9fbe..fcac885 100644
--- a/Makefile.iptrules.in
+++ b/Makefile.iptrules.in
@@ -59,4 +59,4 @@ lib%.so: lib%.oo
 	${AM_V_CCLD}${CCLD} ${AM_LDFLAGS} -shared ${LDFLAGS} -o $@ $< ${libxtables_LIBS} ${LDLIBS};
 
 %.oo: ${XA_SRCDIR}/%.c
-	${AM_V_CC}${CC} ${AM_DEPFLAGS} ${AM_CFLAGS} -DPIC -fPIC ${CFLAGS} -o $@ -c $<;
+	${AM_V_CC}${CC} ${AM_DEPFLAGS} ${AM_CPPFLAGS} ${AM_CFLAGS} -DPIC -fPIC ${CPPFLAGS} ${CFLAGS} -o $@ -c $<;
diff --git a/configure.ac b/configure.ac
index d75ddba..eb682c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,11 +33,11 @@ AC_ARG_WITH([xtlibdir],
 AC_MSG_CHECKING([Xtables module directory])
 AC_MSG_RESULT([$xtlibdir])
 
-regular_CFLAGS="-D_LARGEFILE_SOURCE=1 -D_LARGE_FILES -D_FILE_OFFSET_BITS=64 \
-	-D_REENTRANT -Wall -Waggregate-return -Wmissing-declarations \
+regular_CPPFLAGS="-D_LARGEFILE_SOURCE=1 -D_LARGE_FILES -D_FILE_OFFSET_BITS=64 \
+	-D_REENTRANT -I\${XA_TOPSRCDIR}/include"
+regular_CFLAGS="-Wall -Waggregate-return -Wmissing-declarations \
 	-Wmissing-prototypes -Wredundant-decls -Wshadow -Wstrict-prototypes \
-	-Winline -pipe \
-	-I\${XA_TOPSRCDIR}/include";
+	-Winline -pipe";
 
 #
 # check kernel version
@@ -80,6 +80,7 @@ else
 	fi;
 fi;
 
+AC_SUBST([regular_CPPFLAGS])
 AC_SUBST([regular_CFLAGS])
 AC_SUBST([kbuilddir])
 AC_SUBST([xtlibdir])
diff --git a/extensions/Makefile.am b/extensions/Makefile.am
index 9c9a095..a487fd8 100644
--- a/extensions/Makefile.am
+++ b/extensions/Makefile.am
@@ -1,7 +1,8 @@
 # -*- Makefile -*-
 # AUTOMAKE
 
-AM_CFLAGS = ${regular_CFLAGS} ${libxtables_CFLAGS} -I${abs_top_srcdir}/extensions
+AM_CPPFLAGS = ${regular_CPPFLAGS} -I${abs_top_srcdir}/extensions
+AM_CFLAGS = ${regular_CFLAGS} ${libxtables_CFLAGS}
 
 # Not having Kbuild in Makefile.extra because it will already recurse
 .PHONY: modules modules_install clean_modules
diff --git a/extensions/ipset/Makefile.am b/extensions/ipset/Makefile.am
index b9a7d65..64edf67 100644
--- a/extensions/ipset/Makefile.am
+++ b/extensions/ipset/Makefile.am
@@ -1,7 +1,8 @@
 # -*- Makefile -*-
 
-AM_CFLAGS = ${regular_CFLAGS} -DIPSET_LIB_DIR=\"${xtlibdir}\" \
+AM_CPPFLAGS = ${regular_CPPFLAGS} -DIPSET_LIB_DIR=\"${xtlibdir}\" \
             -DIP_NF_SET_HASHSIZE=1024
+AM_CFLAGS = ${regular_CFLAGS}
 
 include ../../Makefile.extra
 
diff --git a/extensions/ipset/Mbuild b/extensions/ipset/Mbuild
index 40c70c2..92e2f9e 100644
--- a/extensions/ipset/Mbuild
+++ b/extensions/ipset/Mbuild
@@ -4,4 +4,4 @@ obj-m += $(addprefix lib,$(patsubst %.c,%.so,$(notdir \
 	$(wildcard ${XA_SRCDIR}/ipset_*.c))))
 
 libipset_%.oo: ${XA_SRCDIR}/ipset_%.c
-	${AM_V_CC}${CC} ${AM_DEPFLAGS} ${AM_CFLAGS} -DPIC -fPIC ${CFLAGS} -o $@ -c $<;
+	${AM_V_CC}${CC} ${AM_DEPFLAGS} ${AM_CPPFLAGS} ${AM_CFLAGS} -DPIC -fPIC ${CPPFLAGS} ${CFLAGS} -o $@ -c $<;