diff --git a/sys/usb/usbus/cdc/ecm/cdc_ecm_netdev.c b/sys/usb/usbus/cdc/ecm/cdc_ecm_netdev.c
index 65c575869f..ca5b5e73d3 100644
--- a/sys/usb/usbus/cdc/ecm/cdc_ecm_netdev.c
+++ b/sys/usb/usbus/cdc/ecm/cdc_ecm_netdev.c
@@ -59,6 +59,11 @@ static int _send(netdev_t *netdev, const iolist_t *iolist)
     uint8_t *buf = cdcecm->ep_in->ep->buf;
     const iolist_t *iolist_start = iolist;
     size_t len = iolist_size(iolist);
+    /* interface with alternative function ID 1 is the interface containing the
+     * data endpoints, no sense trying to transmit data if it is not active */
+    if (cdcecm->active_iface != 1) {
+        return -ENOTCONN;
+    }
     DEBUG("CDC_ECM_netdev: sending %u bytes\n", len);
     /* load packet data into FIFO */
     size_t iol_offset = 0;