diff --git a/sys/src/9/pc/pc b/sys/src/9/pc/pc
index 73c25d350..68e2e5e33 100644
--- a/sys/src/9/pc/pc
+++ b/sys/src/9/pc/pc
@@ -22,7 +22,7 @@ dev
 
 	ether		netif
 	bridge		netif log
-	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium ptclbsum386 inferno
+	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium inferno
 
 	draw		screen vga vgax swcursor
 	mouse		mouse
diff --git a/sys/src/9/xen/mkfile b/sys/src/9/xen/mkfile
index e7bbe9503..4649210aa 100644
--- a/sys/src/9/xen/mkfile
+++ b/sys/src/9/xen/mkfile
@@ -128,9 +128,6 @@ REPCC=`{../port/mkfilelist ../pc}
 <../port/portmkfile
 <|../port/mkbootrules $CONF
 
-ptclbsum386.$O:	../pc/ptclbsum386.s
-	$AS $AFLAGS ../pc/ptclbsum386.s
-
 # we inherited these.. revisit.
 $ETHER: 	../port/etherif.h ../port/netif.h
 $SDEV:	../port/sd.h
diff --git a/sys/src/9/xen/xenpcf b/sys/src/9/xen/xenpcf
index b6de0768d..a1d83cb02 100644
--- a/sys/src/9/xen/xenpcf
+++ b/sys/src/9/xen/xenpcf
@@ -20,7 +20,7 @@ dev
 
 	xenstore
 	ether		netif
-	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium ptclbsum386 inferno
+	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium inferno
 
 	sd
 
diff --git a/sys/src/libip/mkfile b/sys/src/libip/mkfile
index 5a63a01a7..47c25c4ea 100644
--- a/sys/src/libip/mkfile
+++ b/sys/src/libip/mkfile
@@ -24,3 +24,6 @@ UPDATE=\
 	${LIB:/$objtype/%=/386/%}\
 
 </sys/src/cmd/mksyslib
+
+ptclbsum.8:	ptclbsum386.s
+	$AS -o $target ptclbsum386.s
diff --git a/sys/src/9/pc/ptclbsum386.s b/sys/src/libip/ptclbsum386.s
similarity index 100%
rename from sys/src/9/pc/ptclbsum386.s
rename to sys/src/libip/ptclbsum386.s