diff --git a/config/kernel-bdev-block-device-operations.m4 b/config/kernel-bdev-block-device-operations.m4
index 2805237aa9..28c3032aa4 100644
--- a/config/kernel-bdev-block-device-operations.m4
+++ b/config/kernel-bdev-block-device-operations.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BDEV_BLOCK_DEVICE_OPERATIONS], [
 	AC_MSG_CHECKING([block device operation prototypes])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-bdev-logical-size.m4 b/config/kernel-bdev-logical-size.m4
index d066c863fb..a6194577ab 100644
--- a/config/kernel-bdev-logical-size.m4
+++ b/config/kernel-bdev-logical-size.m4
@@ -8,7 +8,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BDEV_LOGICAL_BLOCK_SIZE], [
 	AC_MSG_CHECKING([whether bdev_logical_block_size() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-bdev-physical-size.m4 b/config/kernel-bdev-physical-size.m4
index 0a1fe8e263..77746ee916 100644
--- a/config/kernel-bdev-physical-size.m4
+++ b/config/kernel-bdev-physical-size.m4
@@ -22,7 +22,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BDEV_PHYSICAL_BLOCK_SIZE], [
 	AC_MSG_CHECKING([whether bdev_physical_block_size() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-end-request.m4 b/config/kernel-blk-end-request.m4
index 0228fb0f9b..ca0a042840 100644
--- a/config/kernel-blk-end-request.m4
+++ b/config/kernel-blk-end-request.m4
@@ -6,7 +6,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_END_REQUEST], [
 	AC_MSG_CHECKING([whether blk_end_request() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-fetch-request.m4 b/config/kernel-blk-fetch-request.m4
index c277f52c08..c4e1146169 100644
--- a/config/kernel-blk-fetch-request.m4
+++ b/config/kernel-blk-fetch-request.m4
@@ -8,7 +8,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_FETCH_REQUEST], [
 	AC_MSG_CHECKING([whether blk_fetch_request() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-discard.m4 b/config/kernel-blk-queue-discard.m4
index 3e5147a519..8306c88ee3 100644
--- a/config/kernel-blk-queue-discard.m4
+++ b/config/kernel-blk-queue-discard.m4
@@ -5,7 +5,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_DISCARD], [
 	AC_MSG_CHECKING([whether blk_queue_discard() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-flush.m4 b/config/kernel-blk-queue-flush.m4
index 06561edf69..261174735d 100644
--- a/config/kernel-blk-queue-flush.m4
+++ b/config/kernel-blk-queue-flush.m4
@@ -12,7 +12,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_FLUSH], [
 	AC_MSG_CHECKING([whether blk_queue_flush() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-io-opt.m4 b/config/kernel-blk-queue-io-opt.m4
index 4ea94e1cdb..fb9b6841b5 100644
--- a/config/kernel-blk-queue-io-opt.m4
+++ b/config/kernel-blk-queue-io-opt.m4
@@ -6,7 +6,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_IO_OPT], [
 	AC_MSG_CHECKING([whether blk_queue_io_opt() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-max-hw-sectors.m4 b/config/kernel-blk-queue-max-hw-sectors.m4
index 7bdf7e0179..2f5515dc6b 100644
--- a/config/kernel-blk-queue-max-hw-sectors.m4
+++ b/config/kernel-blk-queue-max-hw-sectors.m4
@@ -5,7 +5,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_MAX_HW_SECTORS], [
 	AC_MSG_CHECKING([whether blk_queue_max_hw_sectors() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-max-segments.m4 b/config/kernel-blk-queue-max-segments.m4
index 09be121ed1..b2a40423a5 100644
--- a/config/kernel-blk-queue-max-segments.m4
+++ b/config/kernel-blk-queue-max-segments.m4
@@ -6,7 +6,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_MAX_SEGMENTS], [
 	AC_MSG_CHECKING([whether blk_queue_max_segments() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-nonrot.m4 b/config/kernel-blk-queue-nonrot.m4
index 45d78f791f..aa6d678fed 100644
--- a/config/kernel-blk-queue-nonrot.m4
+++ b/config/kernel-blk-queue-nonrot.m4
@@ -8,7 +8,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_NONROT], [
 	AC_MSG_CHECKING([whether blk_queue_nonrot() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-queue-physical-block-size.m4 b/config/kernel-blk-queue-physical-block-size.m4
index c51c81721a..a585b2846b 100644
--- a/config/kernel-blk-queue-physical-block-size.m4
+++ b/config/kernel-blk-queue-physical-block-size.m4
@@ -7,7 +7,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_PHYSICAL_BLOCK_SIZE], [
 	AC_MSG_CHECKING([whether blk_queue_physical_block_size() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-requeue-request.m4 b/config/kernel-blk-requeue-request.m4
index d8e7439e02..286c4b9d0a 100644
--- a/config/kernel-blk-requeue-request.m4
+++ b/config/kernel-blk-requeue-request.m4
@@ -7,7 +7,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_REQUEUE_REQUEST], [
 	AC_MSG_CHECKING([whether blk_requeue_request() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-rq-bytes.m4 b/config/kernel-blk-rq-bytes.m4
index 6430dfe505..a95f8a8ea3 100644
--- a/config/kernel-blk-rq-bytes.m4
+++ b/config/kernel-blk-rq-bytes.m4
@@ -7,7 +7,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_RQ_BYTES], [
 	AC_MSG_CHECKING([whether blk_rq_bytes() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-rq-pos.m4 b/config/kernel-blk-rq-pos.m4
index fd8a92657e..efa595f89b 100644
--- a/config/kernel-blk-rq-pos.m4
+++ b/config/kernel-blk-rq-pos.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_RQ_POS], [
 	AC_MSG_CHECKING([whether blk_rq_pos() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-blk-rq-sectors.m4 b/config/kernel-blk-rq-sectors.m4
index fbcd113204..dea5bb5bac 100644
--- a/config/kernel-blk-rq-sectors.m4
+++ b/config/kernel-blk-rq-sectors.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BLK_RQ_SECTORS], [
 	AC_MSG_CHECKING([whether blk_rq_sectors() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-elevator-change.m4 b/config/kernel-elevator-change.m4
index 90ab51b2eb..ace5aa82d3 100644
--- a/config/kernel-elevator-change.m4
+++ b/config/kernel-elevator-change.m4
@@ -5,7 +5,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_ELEVATOR_CHANGE], [
 	AC_MSG_CHECKING([whether elevator_change() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 		#include <linux/elevator.h>
diff --git a/config/kernel-get-disk-ro.m4 b/config/kernel-get-disk-ro.m4
index aac69b7a10..13ed81217e 100644
--- a/config/kernel-get-disk-ro.m4
+++ b/config/kernel-get-disk-ro.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_GET_DISK_RO], [
 	AC_MSG_CHECKING([whether get_disk_ro() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-rq-for-each_segment.m4 b/config/kernel-rq-for-each_segment.m4
index 182147817f..449168d088 100644
--- a/config/kernel-rq-for-each_segment.m4
+++ b/config/kernel-rq-for-each_segment.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_RQ_FOR_EACH_SEGMENT], [
 	AC_MSG_CHECKING([whether rq_for_each_segment() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[
diff --git a/config/kernel-rq-is_sync.m4 b/config/kernel-rq-is_sync.m4
index 507bf683e0..f6f51c87a0 100644
--- a/config/kernel-rq-is_sync.m4
+++ b/config/kernel-rq-is_sync.m4
@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_KERNEL_RQ_IS_SYNC], [
 	AC_MSG_CHECKING([whether rq_is_sync() is available])
 	tmp_flags="$EXTRA_KCFLAGS"
-	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/blkdev.h>
 	],[