Index: sys/conf/kern.pre.mk
===================================================================
--- sys/conf/kern.pre.mk	(revision 260701)
+++ sys/conf/kern.pre.mk	(working copy)
@@ -6,6 +6,21 @@
 .include <bsd.own.mk>
 .include <bsd.compiler.mk>
 
+# Make sure our TARGET/TARGET_ARCH is compatible
+.if defined(TARGET_ARCH)
+__T=${TARGET_ARCH}
+.else
+__T!= uname -p
+.endif
+.if defined(TARGET)
+__TT=${TARGET}
+.else
+__TT!=uname -m
+.endif
+.if ${__TT} != ${MACHINE} || ${__T} != ${MACHINE_ARCH}
+.error Invalid combination, trying to build kernel ${MACHINE}/${MACHINE_ARCH} using ${__TT}/${__T}
+.endif
+
 # backwards compat option for older systems.
 MACHINE_CPUARCH?=${MACHINE_ARCH:C/mips(n32|64)?(el)?/mips/:C/arm(v6)?(eb)?/arm/:C/powerpc64/powerpc/}