diff --git a/xen/arch/arm/device.c b/xen/arch/arm/device.c
index b11366d722..ad50838b9f 100644
--- a/xen/arch/arm/device.c
+++ b/xen/arch/arm/device.c
@@ -89,7 +89,7 @@ int __overlay_init map_range_to_domain(const struct dt_device_node *dev,
     {
         res = map_regions_p2mt(d,
                                gaddr_to_gfn(addr),
-                               PFN_UP(len),
+                               PFN_UP(addr + len) - PFN_DOWN(addr),
                                maddr_to_mfn(addr),
                                mr_data->p2mt);