diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index c657a9871483..b9dad88b8ea3 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -535,7 +535,7 @@ static unsigned long init_altmap_base(resource_size_t base)
 
 static unsigned long init_altmap_reserve(resource_size_t base)
 {
-	unsigned long reserve = PHYS_PFN(SZ_8K);
+	unsigned long reserve = PFN_UP(SZ_8K);
 	unsigned long base_pfn = PHYS_PFN(base);
 
 	reserve += base_pfn - PFN_SECTION_ALIGN_DOWN(base_pfn);