diff --git a/share/mk/sys.mk b/share/mk/sys.mk
index a185f6ea31ac..9af08337e473 100644
--- a/share/mk/sys.mk
+++ b/share/mk/sys.mk
@@ -1,5 +1,5 @@
 #	from: @(#)sys.mk	8.2 (Berkeley) 3/21/94
-#	$Id: sys.mk,v 1.26 1997/09/05 11:45:15 peter Exp $
+#	$Id: sys.mk,v 1.27 1998/01/13 06:00:54 jb Exp $
 
 unix		?=	We run FreeBSD, not UNIX.
 
@@ -94,8 +94,15 @@ YFLAGS		?=
 YFLAGS		?=	-d
 .endif
 
+# FreeBSD/i386 as traditionally been built with a version of make
+# which knows MACHINE, but not MACHINE_ARCH. When building on other
+# architectures, assume that the version of make being used has an
+# explicit MACHINE_ARCH setting and treat a missing MACHINE_ARCH
+# as an i386 architecture.
+MACHINE_ARCH?=	i386
+
 # Default executable format
-.if ${MACHINE} == "alpha"
+.if ${MACHINE_ARCH} == "alpha"
 BINFORMAT	?=	elf
 .else
 BINFORMAT	?=	aout