diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 3e7b11cf1aae..cb98b8fe786e 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -655,6 +655,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	resource_size_t start, size;
 	struct nd_region *nd_region;
 	unsigned long npfns, align;
+	u32 end_trunc;
 	struct nd_pfn_sb *pfn_sb;
 	phys_addr_t offset;
 	const char *sig;
@@ -696,6 +697,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	size = resource_size(&nsio->res);
 	npfns = PHYS_PFN(size - SZ_8K);
 	align = max(nd_pfn->align, (1UL << SUBSECTION_SHIFT));
+	end_trunc = start + size - ALIGN_DOWN(start + size, align);
 	if (nd_pfn->mode == PFN_MODE_PMEM) {
 		/*
 		 * The altmap should be padded out to the block size used
@@ -714,7 +716,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 		return -ENXIO;
 	}
 
-	npfns = PHYS_PFN(size - offset);
+	npfns = PHYS_PFN(size - offset - end_trunc);
 	pfn_sb->mode = cpu_to_le32(nd_pfn->mode);
 	pfn_sb->dataoff = cpu_to_le64(offset);
 	pfn_sb->npfns = cpu_to_le64(npfns);
@@ -723,6 +725,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
 	pfn_sb->version_major = cpu_to_le16(1);
 	pfn_sb->version_minor = cpu_to_le16(3);
+	pfn_sb->end_trunc = cpu_to_le32(end_trunc);
 	pfn_sb->align = cpu_to_le32(nd_pfn->align);
 	checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
 	pfn_sb->checksum = cpu_to_le64(checksum);