diff --git a/src/mkmk.sh b/src/mkmk.sh
index 37c43926..7d6b8657 100644
--- a/src/mkmk.sh
+++ b/src/mkmk.sh
@@ -72,6 +72,7 @@ cd lib9
 9c  seek.c
 9c  sendfd.c
 9c  sleep.c
+9c  strdup.c
 9c  strecpy.c
 9c  sysfatal.c
 9c  sysname.c