diff --git a/hw/isa/piix3.c b/hw/isa/piix3.c
index 5e8ac98ae0..0549e043ca 100644
--- a/hw/isa/piix3.c
+++ b/hw/isa/piix3.c
@@ -322,6 +322,7 @@ static void pci_piix3_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
     AcpiDevAmlIfClass *adevc = ACPI_DEV_AML_IF_CLASS(klass);
 
+    k->config_write = piix3_write_config;
     dc->reset       = piix3_reset;
     dc->desc        = "ISA bridge";
     dc->vmsd        = &vmstate_piix3;
@@ -371,7 +372,6 @@ static void piix3_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
-    k->config_write = piix3_write_config;
     k->realize = piix3_realize;
 }
 
@@ -385,7 +385,6 @@ static void piix3_xen_class_init(ObjectClass *klass, void *data)
 {
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
-    k->config_write = piix3_write_config;
     k->realize = piix3_realize;
 }