diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7aa11a6..43cfaab 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -44,6 +44,8 @@
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 
+extern unsigned long sysctl_user_reserve_kbytes;
+
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 
 /* to align the pointer to the (next) page boundary */