--- Makefile
+++ Makefile
@@ -11,15 +11,9 @@
 # Standard part of Makefile for topdir.
 TOPLEVEL_INCLUDED=YES
 
-# For recent kernels we only need the source in KERNEL_DIR to build. Older
-# kernels have a bug, where linux/netfilter_ipv4.h includes linux/config.h,
-# which includes linux/autoconf.h, which is placed into KBUILD_OUTPUT.
 ifndef KERNEL_DIR
 KERNEL_DIR="/lib/modules/$(shell uname -r)/source"
 endif
-ifndef KBUILD_OUTPUT
-KBUILD_OUTPUT="/lib/modules/$(shell uname -r)/build"
-endif
 IPTABLES_VERSION:=1.4.0
 OLD_IPTABLES_VERSION:=1.4.0rc1
 
@@ -42,8 +36,8 @@
 DO_SELINUX=0
 endif
 
-COPT_FLAGS:=-O2
-CFLAGS:=$(COPT_FLAGS) -Wall -Wunused -I$(KBUILD_OUTPUT)/include -I$(KERNEL_DIR)/include -Iinclude/ -DIPTABLES_VERSION=\"$(IPTABLES_VERSION)\" #-g -DDEBUG #-pg # -DIPTC_DEBUG
+COPT_FLAGS:=$(CFLAGS)
+CFLAGS:=$(COPT_FLAGS) -Wall -Wunused -idirafter $(KERNEL_DIR)/include -Iinclude/ -DIPTABLES_VERSION=\"$(IPTABLES_VERSION)\"
 
 ifdef NO_SHARED_LIBS
 CFLAGS += -DNO_SHARED_LIBS=1