diff --git a/sys/conf/kern.post.mk b/sys/conf/kern.post.mk
index d08dfe30d7de..7aac581fdb0f 100644
--- a/sys/conf/kern.post.mk
+++ b/sys/conf/kern.post.mk
@@ -351,8 +351,6 @@ ${__obj}: ${OBJS_DEPEND_GUESS.${__obj}}
 
 .depend: .PRECIOUS ${SRCS}
 
-_MAP_DEBUG_PREFIX= yes
-
 _ILINKS= machine
 .if ${MACHINE} != ${MACHINE_CPUARCH} && ${MACHINE} != "arm64"
 _ILINKS+= ${MACHINE_CPUARCH}
@@ -370,13 +368,11 @@ _ILINKS+= i386
 .if !exists(${.OBJDIR}/${_link})
 ${SRCS} ${DEPENDOBJS}: ${_link}
 .endif
-.if defined(_MAP_DEBUG_PREFIX)
 .if ${_link} == "machine"
 CFLAGS+= -fdebug-prefix-map=./machine=${SYSDIR}/${MACHINE}/include
 .else
 CFLAGS+= -fdebug-prefix-map=./${_link}=${SYSDIR}/${_link}/include
 .endif
-.endif
 .endfor
 
 ${_ILINKS}:
diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
index ace2f4cc3d4c..89da3d4fc82e 100644
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -281,8 +281,6 @@ ${FULLPROG}: ${OBJS} ${BLOB_OBJS}
 	${OBJCOPY} --strip-debug ${.TARGET}
 .endif
 
-_MAP_DEBUG_PREFIX= yes
-
 _ILINKS=machine
 .if ${MACHINE_CPUARCH} == "i386" || ${MACHINE_CPUARCH} == "amd64"
 _ILINKS+=x86
@@ -304,13 +302,11 @@ beforebuild: ${_ILINKS}
 .if !exists(${.OBJDIR}/${_link})
 OBJS_DEPEND_GUESS+=	${_link}
 .endif
-.if defined(_MAP_DEBUG_PREFIX)
 .if ${_link} == "machine"
 CFLAGS+= -fdebug-prefix-map=./machine=${SYSDIR}/${MACHINE}/include
 .else
 CFLAGS+= -fdebug-prefix-map=./${_link}=${SYSDIR}/${_link}/include
 .endif
-.endif
 .endfor
 
 .NOPATH: ${_ILINKS}