diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index e4451d1..878d7ac 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -33,6 +33,7 @@
 };
 
 extern struct ipc_namespace init_ipc_ns;
+extern atomic_t nr_ipc_ns;
 
 #ifdef CONFIG_SYSVIPC
 #define INIT_IPC_NS(ns)		.ns		= &init_ipc_ns,