diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 5c0635a..73d3c84 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1221,7 +1221,7 @@
 
 	/* Get mfn list */
 	if (!xen_feature(XENFEAT_auto_translated_physmap))
-		phys_to_machine_mapping = (unsigned long *)xen_start_info->mfn_list;
+		xen_build_dynamic_phys_to_machine();
 
 	pgd = (pgd_t *)xen_start_info->pt_base;