diff --git a/hw/pci.h b/hw/pci.h
index 113e556e2d..7d56337c2b 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -16,6 +16,7 @@
 #define PCI_DEVFN(slot, func)   ((((slot) & 0x1f) << 3) | ((func) & 0x07))
 #define PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
 #define PCI_FUNC(devfn)         ((devfn) & 0x07)
+#define PCI_SLOT_MAX            32
 #define PCI_FUNC_MAX            8
 
 /* Class, Vendor and Device IDs from Linux's pci_ids.h */
diff --git a/hw/pci_internals.h b/hw/pci_internals.h
index e3c93a3cc5..efaefcded8 100644
--- a/hw/pci_internals.h
+++ b/hw/pci_internals.h
@@ -22,7 +22,7 @@ struct PCIBus {
     pci_hotplug_fn hotplug;
     DeviceState *hotplug_qdev;
     void *irq_opaque;
-    PCIDevice *devices[256];
+    PCIDevice *devices[PCI_SLOT_MAX * PCI_FUNC_MAX];
     PCIDevice *parent_dev;
     target_phys_addr_t mem_base;