diff --git a/doc/changelog.txt b/doc/changelog.txt
index 1b43499..ccbb93e 100644
--- a/doc/changelog.txt
+++ b/doc/changelog.txt
@@ -1,6 +1,7 @@
 
 HEAD
 ====
+- xt_CHECKSUM: abort build when the feature is already provided by mainline
 - xt_TARPIT: fix kernel warning about RTAX_HOPLIMIT being used
 - xt_TEE: abort build when the feature is already provided by mainline
 - xt_psd: restore functionality with UDP
diff --git a/extensions/xt_CHECKSUM.c b/extensions/xt_CHECKSUM.c
index 548860c..f565d82 100644
--- a/extensions/xt_CHECKSUM.c
+++ b/extensions/xt_CHECKSUM.c
@@ -12,6 +12,13 @@
 #include <linux/module.h>
 #include <linux/skbuff.h>
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
+#	error ----------------------------------------------------------
+#	error This module has been merged into, and is available in the
+#	error mainline since Linux kernel v2.6.36. Please use that.
+#	error ----------------------------------------------------------
+#endif
+
 #include <linux/netfilter/x_tables.h>
 #include "xt_CHECKSUM.h"
 #include "compat_xtables.h"