diff --git a/include/asm-x86/pgtable_64.h b/include/asm-x86/pgtable_64.h
index bd4740a..7fd5e0e 100644
--- a/include/asm-x86/pgtable_64.h
+++ b/include/asm-x86/pgtable_64.h
@@ -246,6 +246,7 @@
 #define __swp_entry_to_pte(x)		((pte_t) { .pte = (x).val })
 
 extern int kern_addr_valid(unsigned long addr); 
+extern void cleanup_highmap(void);
 
 #define io_remap_pfn_range(vma, vaddr, pfn, size, prot)		\
 		remap_pfn_range(vma, vaddr, pfn, size, prot)