diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
index 435654ffa4a0..2038acbcfd2a 100644
--- a/arch/alpha/kernel/pci-sysfs.c
+++ b/arch/alpha/kernel/pci-sysfs.c
@@ -173,8 +173,11 @@ int pci_mmap_legacy_page_range(struct pci_bus *bus, struct vm_area_struct *vma,
 	int sparse = has_sparse(hose, mmap_type);
 	unsigned long res_size;
 
-	res_size = (mmap_type == pci_mmap_mem) ? bus->legacy_mem->size :
-						 bus->legacy_io->size;
+	res_size = (mmap_type == pci_mmap_mem) ? PCI_LEGACY_MEM_SIZE :
+						 PCI_LEGACY_IO_SIZE;
+	if (sparse)
+		res_size <<= 5;
+
 	if (!__legacy_mmap_fits(vma, res_size))
 		return -EINVAL;