diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 0313a5e..d9249a8 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1014,6 +1014,9 @@
 	init_pg_tables_start = __pa(pg0);
 	init_pg_tables_end = __pa(pg0);
 
+	/* As described in head_32.S, we map the first 128M of memory. */
+	max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
+
 	/* Load the %fs segment register (the per-cpu segment register) with
 	 * the normal data segment to get through booting. */
 	asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");