diff --git a/src/usb.c b/src/usb.c
index ec502c9..8bdb8d6 100644
--- a/src/usb.c
+++ b/src/usb.c
@@ -278,6 +278,9 @@
 
 	n = libusb_get_port_numbers(dev, port_numbers, sizeof(port_numbers));
 
+	if (n < 1)
+		return SR_ERR;
+
 	len = snprintf(path, path_len, "usb/%d-%d",
 	               libusb_get_bus_number(dev), port_numbers[0]);