diff --git a/sys/src/9/mkfile b/sys/src/9/mkfile
index 9208a7b94..d4e9a7228 100644
--- a/sys/src/9/mkfile
+++ b/sys/src/9/mkfile
@@ -3,11 +3,13 @@ ARCH=\
 	bcm64\
 	cycv\
 	kw\
-	mtx\
+#	power arch:\
+#	mtx\
 	omap\
 	pc\
 	pc64\
-	ppc\
+#	power arch:\
+#	ppc\
 	sgi\
 	teg2\
 	xen\
diff --git a/sys/src/boot/zynq/mkfile b/sys/src/boot/zynq/mkfile
index 90f503446..2dd24c711 100644
--- a/sys/src/boot/zynq/mkfile
+++ b/sys/src/boot/zynq/mkfile
@@ -7,6 +7,9 @@ TEXTBASE=0xfffc0000
 
 all:V: $TARG
 
+install:V:
+	echo install not supported >[1=2]
+
 clean:V:
 	rm -rf $TARG *.$O
 	@{objtype=$cputype mk -f mkfile.port clean}
diff --git a/sys/src/mkfile b/sys/src/mkfile
index 00c1800c8..7711200b6 100644
--- a/sys/src/mkfile
+++ b/sys/src/mkfile
@@ -1,5 +1,12 @@
 </$objtype/mkfile
 
+SUPPORTED_OBJS=\
+	386\
+	amd64\
+	arm\
+	arm64\
+	mips\
+
 LIBS=\
 	lib9p\
 	libString\
@@ -52,21 +59,29 @@ none:VQ:
 
 all install clean nuke:VQ:
 	date
-	for (i in $LIBS $SUBSYS $CMDS) @{
-		cd $i
-		mk $target
+	if (~ $objtype $SUPPORTED_OBJS) {
+		for (i in $LIBS $SUBSYS $CMDS) @{
+			cd $i
+			mk $target
+		}
 	}
+	if not
+		echo $objtype arch not supported by 9front >[1=2]
 	date
 
 installall:V:
 	echo "installall not supported"
 
 release:V:
-	mk nuke
-	rm -f /$objtype/lib/ape/*.a
-	rm -f /$objtype/lib/*.a
-	mk install
-	mk clean
+	if (~ $objtype $SUPPORTED_OBJS) {
+		mk nuke
+		rm -f /$objtype/lib/ape/*.a
+		rm -f /$objtype/lib/*.a
+		mk install
+		mk clean
+	}
+	if not
+		echo $objtype architecture not supported >[1=2]
 
 kernels:V:
 	for (i in 9 boot) @{