diff --git a/src/nm-device.c b/src/nm-device.c
index 53eece87f6..e443663407 100644
--- a/src/nm-device.c
+++ b/src/nm-device.c
@@ -423,7 +423,7 @@ nm_device_set_ip_iface (NMDevice *self, const char *iface)
 	priv->ip_iface = g_strdup (iface);
 	if (priv->ip_iface) {
 		priv->ip_ifindex = nm_netlink_iface_to_index (priv->ip_iface);
-		if (!priv->ip_ifindex) {
+		if (priv->ip_ifindex < 0) {
 			nm_log_warn (LOGD_HW, "(%s): failed to look up interface index", iface);
 		}
 	}
diff --git a/src/vpn-manager/nm-vpn-connection.c b/src/vpn-manager/nm-vpn-connection.c
index 73f2b553c5..d4b551895f 100644
--- a/src/vpn-manager/nm-vpn-connection.c
+++ b/src/vpn-manager/nm-vpn-connection.c
@@ -452,7 +452,7 @@ nm_vpn_connection_ip4_config_get (DBusGProxy *proxy,
 
 	/* Grab the interface index for address/routing operations */
 	priv->ip_ifindex = nm_netlink_iface_to_index (priv->ip_iface);
-	if (!priv->ip_ifindex) {
+	if (priv->ip_ifindex < 0) {
 		nm_log_err (LOGD_VPN, "(%s): failed to look up VPN interface index", priv->ip_iface);
 		goto error;
 	}