diff --git a/hw/pc.c b/hw/pc.c
index 20dc7fd..88478e7 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -880,7 +880,10 @@ void pc_memory_init(ram_addr_t ram_size,
         isa_bios_size = 128 * 1024;
     cpu_register_physical_memory(0x100000 - isa_bios_size,
                                  isa_bios_size,
-                                 (bios_offset + bios_size - isa_bios_size) | IO_MEM_ROM);
+                                 qemu_ram_alloc(isa_bios_size));
+    cpu_physical_memory_write_rom(0x100000 - isa_bios_size,
+                                  qemu_get_ram_ptr(bios_offset + bios_size - isa_bios_size),
+                                  isa_bios_size);
 
     option_rom_offset = qemu_ram_alloc(PC_ROM_SIZE);
     cpu_register_physical_memory(PC_ROM_MIN_VGA, PC_ROM_SIZE, option_rom_offset);