diff --git a/kernel/timer.c b/kernel/timer.c
index fd74268..074b4bd 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -33,6 +33,7 @@
 #include <linux/posix-timers.h>
 #include <linux/cpu.h>
 #include <linux/syscalls.h>
+#include <linux/delay.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>