diff --git a/include/linux/sync.h b/include/linux/sync.h
index 38ea986dc70f..5f493638148d 100644
--- a/include/linux/sync.h
+++ b/include/linux/sync.h
@@ -19,6 +19,7 @@
 #include <linux/kref.h>
 #include <linux/ktime.h>
 #include <linux/list.h>
+#include <linux/seq_file.h>
 #include <linux/spinlock.h>
 #include <linux/wait.h>