diff --git a/include/pci.h b/include/pci.h
index 5fb212cab1..508f7bca81 100644
--- a/include/pci.h
+++ b/include/pci.h
@@ -405,6 +405,7 @@
 #define  PCI_MSI_FLAGS_QSIZE	0x70	/* Message queue size configured */
 #define  PCI_MSI_FLAGS_QMASK	0x0e	/* Maximum queue size available */
 #define  PCI_MSI_FLAGS_ENABLE	0x01	/* MSI feature enabled */
+#define  PCI_MSI_FLAGS_MASKBIT	0x0100	/* Per-vector masking capable */
 #define PCI_MSI_RFU		3	/* Rest of capability flags */
 #define PCI_MSI_ADDRESS_LO	4	/* Lower 32 bits */
 #define PCI_MSI_ADDRESS_HI	8	/* Upper 32 bits (if PCI_MSI_FLAGS_64BIT set) */