diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index fa895fc..9944379 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -35,6 +35,7 @@
 #include <linux/interrupt.h>
 #include <linux/slab.h>
 #include <linux/time.h>
+#include <linux/mutex.h>
 
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>