diff --git a/lib/usb-device-wrapper.ts b/lib/usb-device-wrapper.ts
index 065ecb6..73c1211 100644
--- a/lib/usb-device-wrapper.ts
+++ b/lib/usb-device-wrapper.ts
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 import * as dapjs from "dapjs";
+// dapjs import faff needed for use from Node such as Vitest https://github.com/ARMmbed/dapjs/issues/118
 import type { CortexM, DAPLink, WebUSB } from "dapjs";
 const {
   CortexM: CortexMValue,
diff --git a/lib/usb-partial-flashing.ts b/lib/usb-partial-flashing.ts
index 1b9de27..0074d37 100644
--- a/lib/usb-partial-flashing.ts
+++ b/lib/usb-partial-flashing.ts
@@ -44,6 +44,8 @@
  * Latest Microsoft implementation is here:
  * https://github.com/microsoft/pxt-microbit/blob/master/editor/flash.ts
  */
+
+// dapjs import faff needed for Vitest https://github.com/ARMmbed/dapjs/issues/118
 import * as dapjs from "dapjs";
 const { DAPLink: DAPLinkValue } = dapjs;
 import { Logging } from "./logging.js";