Index: UPDATING
===================================================================
--- UPDATING
+++ UPDATING
@@ -26,6 +26,14 @@
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20191120:
+	Defining the long deprected NO_CTF, NO_DEBUG_FILES, NO_INSTALLLIB,
+	NO_MAN, NO_PROFILE, and NO_WARNS variables is now an error.  Update
+	your Makefiles and scripts to define MK_<var>=no instead as required.
+
+	One exception to this is that program or libary Makefiles should
+	define MAN to empty rather than setting MK_MAN=no.
+
 20191107:
 	The nctgpio and wbwd drivers have been moved to the superio bus.
 	If you have one of these drivers in a kernel configuration, then
Index: share/mk/bsd.opts.mk
===================================================================
--- share/mk/bsd.opts.mk
+++ share/mk/bsd.opts.mk
@@ -100,7 +100,7 @@
     PROFILE \
     WARNS
 .if defined(NO_${var})
-.warning "NO_${var} is defined, but deprecated. Please use MK_${var}=no instead."
+.error "NO_${var} is defined, but deprecated. Please use MK_${var}=no instead."
 MK_${var}:=no
 .endif
 .endfor