diff --git a/kernel/async.c b/kernel/async.c
index 27235f5..15319d6 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -56,6 +56,7 @@
 #include <linux/init.h>
 #include <linux/kthread.h>
 #include <linux/delay.h>
+#include <linux/slab.h>
 #include <asm/atomic.h>
 
 static async_cookie_t next_cookie = 1;