diff --git a/mm/memory.c b/mm/memory.c
index 06ff072..01d0289 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -884,7 +884,7 @@
 	return 0;
 }
 
-int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		   pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
 		   unsigned long addr, unsigned long end)
 {