diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 952217572113..b2e8322755c1 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -14,7 +14,7 @@
 #include <linux/delay.h>
 #include "pci.h"
 
-#define VIRTFN_ID_LEN	16
+#define VIRTFN_ID_LEN	17	/* "virtfn%u\0" for 2^32 - 1 */
 
 int pci_iov_virtfn_bus(struct pci_dev *dev, int vf_id)
 {