diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index b60f2b6..ec62a05 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -24,6 +24,7 @@
 
 #include <linux/cache.h>
 #include <linux/spinlock.h>
+#include <linux/rtmutex.h>
 #include <linux/threads.h>
 #include <linux/cpumask.h>
 #include <linux/seqlock.h>