diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 524355a8b4be..58e41d95d029 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -1364,7 +1364,10 @@ static int vntb_epf_peer_mw_count(struct ntb_dev *ntb)
 
 static u64 vntb_epf_db_valid_mask(struct ntb_dev *ntb)
 {
-	return BIT_ULL(ntb_ndev(ntb)->db_count) - 1;
+	if (ntb_ndev(ntb)->db_count < EPF_IRQ_DB_START)
+		return 0;
+
+	return BIT_ULL(ntb_ndev(ntb)->db_count - EPF_IRQ_DB_START) - 1;
 }
 
 static int vntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)