diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -43,11 +43,7 @@
 CWARNEXTRA+=	-Wno-error=shift-negative-value
 CWARNEXTRA+=	-Wno-address-of-packed-member
 .if ${COMPILER_VERSION} >= 130000
-.if ${MK_SET_BUT_NOTUSED_KERNEL_WARNINGS} == "no"
-CWARNEXTRA+=	${NO_WUNUSED_BUT_SET_VARIABLE}
-.else
-CWARNEXTRA+=	-Wno-error=unused-but-set-variable
-.endif
+CWARNFLAGS+=	-Wno-error=unused-but-set-variable
 .endif
 .endif	# clang
 
diff --git a/sys/conf/kern.opts.mk b/sys/conf/kern.opts.mk
--- a/sys/conf/kern.opts.mk
+++ b/sys/conf/kern.opts.mk
@@ -60,8 +60,7 @@
     INIT_ALL_ZERO \
     KERNEL_RETPOLINE \
     RATELIMIT \
-    REPRODUCIBLE_BUILD \
-    SET_BUT_NOTUSED_KERNEL_WARNINGS
+    REPRODUCIBLE_BUILD
 
 # Some options are totally broken on some architectures. We disable
 # them. If you need to enable them on an experimental basis, you