Some day I will get this right.

src/mkfile

diff --git a/src/mkfile b/src/mkfile
index 296978c..75fe111 100644
--- a/src/mkfile
+++ b/src/mkfile
@@ -37,7 +37,12 @@
 			(cd $i; mk -n -a install)
 			echo cd ..
 		done
-	) | sed 's/'$SYSNAME'/$SYSNAME/; s/'$OBJTYPE'/$OBJTYPE/' >$target
+	) | sed '
+		s/'$SYSNAME'/$SYSNAME/g
+		s/'$OBJTYPE'/$OBJTYPE/g
+		s/9[ac] *getcallerpc-.*/9a getcallerpc-$OBJTYPE.s || 9c getcallerpc-$OBJTYPE.c/
+		s/^9[ac] *tas-.*/9a tas-$OBJTYPE.s || 9c tas-$OBJTYPE.c/
+	' >$target
 
 testmkmk:V:
 	mk mkmk.sh

src/mkmk.sh

diff --git a/src/mkmk.sh b/src/mkmk.sh
index 844d343..52d58b4 100644
--- a/src/mkmk.sh
+++ b/src/mkmk.sh
@@ -67,7 +67,7 @@
 9c  sleep.c
 9c  strecpy.c
 9c  sysfatal.c
-9a tas-$SYSNAME.s || 9c tas-$SYSNAME.c
+9a tas-$OBJTYPE.s || 9c tas-$OBJTYPE.c
 9c  time.c
 9c  tokenize.c
 9c  u16.c