diff --git a/mm/memremap.c b/mm/memremap.c
index 68204912cc0a..03ccbdfeb697 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -103,6 +103,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
 void memunmap_pages(struct dev_pagemap *pgmap)
 {
 	struct resource *res = &pgmap->res;
+	struct page *first_page;
 	unsigned long pfn;
 	int nid;
 
@@ -111,14 +112,16 @@ void memunmap_pages(struct dev_pagemap *pgmap)
 		put_page(pfn_to_page(pfn));
 	dev_pagemap_cleanup(pgmap);
 
+	/* make sure to access a memmap that was actually initialized */
+	first_page = pfn_to_page(pfn_first(pgmap));
+
 	/* pages are dead and unused, undo the arch mapping */
-	nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
+	nid = page_to_nid(first_page);
 
 	mem_hotplug_begin();
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
-		pfn = PHYS_PFN(res->start);
-		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
-				 PHYS_PFN(resource_size(res)), NULL);
+		__remove_pages(page_zone(first_page), PHYS_PFN(res->start),
+			       PHYS_PFN(resource_size(res)), NULL);
 	} else {
 		arch_remove_memory(nid, res->start, resource_size(res),
 				pgmap_altmap(pgmap));