diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index d0cc62b..a97314c 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/sched.h>
+#include <linux/slab.h>
 #include <linux/sort.h>
 #include "ctree.h"
 #include "ref-cache.h"