diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
index 10e6e7c2ab..de932286b5 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -192,6 +192,12 @@ static int pxb_map_irq_fn(PCIDevice *pci_dev, int pin)
 {
     PCIDevice *pxb = pci_get_bus(pci_dev)->parent_dev;
 
+    /*
+     * First carry out normal swizzle to handle
+     * multple root ports on a pxb instance.
+     */
+    pin = pci_swizzle_map_irq_fn(pci_dev, pin);
+
     /*
      * The bios does not index the pxb slot number when
      * it computes the IRQ because it resides on bus 0