diff --git a/src/libmach/8.c b/src/libmach/8.c
index 07ec305057b..34248e6f33a 100644
--- a/src/libmach/8.c
+++ b/src/libmach/8.c
@@ -30,6 +30,7 @@
  * 386 definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include <ureg_x86.h>
 #include <mach.h>