diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 57e545b84bf199cb8db2b2fbefa0d4755a419394..097b288779e2e19467bf061f7d42ade9f827516f 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -337,8 +337,9 @@ void __init mem_init(void)
 
 		highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
 		for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
+			phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
 			struct page *page = pfn_to_page(pfn);
-			if (memblock_is_reserved(pfn << PAGE_SHIFT))
+			if (memblock_is_reserved(paddr))
 				continue;
 			ClearPageReserved(page);
 			init_page_count(page);