diff --git a/fs/hppfs/hppfs.c b/fs/hppfs/hppfs.c
index 826c3f9d29ac665f11f66d2c83c1922041629137..943ce751ce19bd121f811ceaea151dc1c79eee0d 100644
--- a/fs/hppfs/hppfs.c
+++ b/fs/hppfs/hppfs.c
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/statfs.h>
 #include <linux/types.h>
+#include <linux/pid_namespace.h>
 #include <asm/uaccess.h>
 #include "os.h"