diff --git a/sys/conf/Makefile.amd64 b/sys/conf/Makefile.amd64
--- a/sys/conf/Makefile.amd64
+++ b/sys/conf/Makefile.amd64
@@ -29,8 +29,6 @@
 .endif
 .include "$S/conf/kern.pre.mk"
 
-INCLUDES+= -I$S/contrib/libfdt
-
 .if !empty(DDB_ENABLED) || !empty(DTRACE_ENABLED) || !empty(HWPMC_ENABLED)
 CFLAGS+=	-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
 .endif
diff --git a/sys/conf/Makefile.arm b/sys/conf/Makefile.arm
--- a/sys/conf/Makefile.arm
+++ b/sys/conf/Makefile.arm
@@ -27,8 +27,6 @@
 .endif
 .include "$S/conf/kern.pre.mk"
 
-INCLUDES+= -I$S/contrib/libfdt -I$S/contrib/device-tree/include -I$S/dts/include
-
 LINUX_DTS_VERSION!=	awk '/freebsd,dts-version/ { sub(/;$$/,"", $$NF); print $$NF }' $S/dts/freebsd-compatible.dts
 CFLAGS += -DLINUX_DTS_VERSION=\"${LINUX_DTS_VERSION}\"
 
diff --git a/sys/conf/Makefile.arm64 b/sys/conf/Makefile.arm64
--- a/sys/conf/Makefile.arm64
+++ b/sys/conf/Makefile.arm64
@@ -23,8 +23,6 @@
 .endif
 .include "$S/conf/kern.pre.mk"
 
-INCLUDES+= -I$S/contrib/libfdt -I$S/contrib/device-tree/include
-
 LINUX_DTS_VERSION!=	awk '/freebsd,dts-version/ { sub(/;$$/,"", $$NF); print $$NF }' $S/dts/freebsd-compatible.dts
 CFLAGS += -DLINUX_DTS_VERSION=\"${LINUX_DTS_VERSION}\"
 
diff --git a/sys/conf/Makefile.i386 b/sys/conf/Makefile.i386
--- a/sys/conf/Makefile.i386
+++ b/sys/conf/Makefile.i386
@@ -27,8 +27,6 @@
 .endif
 .include "$S/conf/kern.pre.mk"
 
-INCLUDES+= -I$S/contrib/libfdt
-
 %BEFORE_DEPEND
 
 %OBJS
diff --git a/sys/conf/Makefile.riscv b/sys/conf/Makefile.riscv
--- a/sys/conf/Makefile.riscv
+++ b/sys/conf/Makefile.riscv
@@ -24,8 +24,6 @@
 .endif
 .include "$S/conf/kern.pre.mk"
 
-INCLUDES+= -I$S/contrib/libfdt -I$S/contrib/device-tree/include
-
 # Set the ELF LMA to the address that OpenSBI's fw_jump jumps to. This allows
 # us to load the kernel with the -kernel flag in QEMU without having to embed
 # it inside BBL or OpenSBI's fw_payload first.
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -70,6 +70,12 @@
 
 INCLUDES= ${NOSTDINC} ${INCLMAGIC} -I. -I$S -I$S/contrib/ck/include
 
+INCLUDES+=	-I$S/contrib/libfdt
+.if ${MK_FDT} != "no"
+INCLUDES+=	-I$S/contrib/device-tree/include \
+		-I$S/dts/include
+.endif
+
 CFLAGS=	${COPTFLAGS} ${DEBUG}
 CFLAGS+= ${INCLUDES} -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h
 CFLAGS_PARAM_INLINE_UNIT_GROWTH?=100
diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -134,6 +134,12 @@
 # set because there are no standard paths for non-headers.
 CFLAGS+=	-I. -I${SYSDIR} -I${SYSDIR}/contrib/ck/include
 
+.if !empty(OPT_FDT)
+CFLAGS+=	-I${SYSDIR}/contrib/libfdt \
+		-I${SYSDIR}/contrib/device-tree/include \
+		-I${SYSDIR}/dts/include
+.endif
+
 CFLAGS.gcc+=	-finline-limit=${INLINE_LIMIT}
 CFLAGS.gcc+=	-fms-extensions
 CFLAGS.gcc+= --param inline-unit-growth=100