diff --git a/UPDATING b/UPDATING
index c997dab2c7b5..ce0f9be9aaf9 100644
--- a/UPDATING
+++ b/UPDATING
@@ -53,7 +53,9 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 12.x IS SLOW:
 
 20171005:
 	The arm port has split armv6 into armv6 and armv7. armv7 is now
-	a valid TARGET_ARCH/MACHINE_ARCH setting.
+	a valid TARGET_ARCH/MACHINE_ARCH setting. If you have an armv7 system
+	and are running a kernel from before r324363, you will need to add
+	MACHINE_ARCH=armv7 to 'make buildworld' to do a native build.
 
 20171003:
 	When building multiple kernels using KERNCONF, non-existent KERNCONF