diff --git a/exercise-book/src/nrf52-usb-unknown-requests.md b/exercise-book/src/nrf52-usb-unknown-requests.md
index e180e58..60f9463 100644
--- a/exercise-book/src/nrf52-usb-unknown-requests.md
+++ b/exercise-book/src/nrf52-usb-unknown-requests.md
@@ -6,4 +6,4 @@ For this situation, the USB specification defines a device-side procedure for "s
 
 > This procedure should be used to deal with invalid requests, requests whose `SETUP` stage doesn't match any USB 2.0 standard request, and requests not supported by the device – for instance the `SET_DESCRIPTOR` request is not mandatory.
 
-✅ Use the `dk::usbd::ep0stall()` helper function to stall endpoint 0 in `nrf52-code/usb-app/src/bin/usb-4.rs`
+✅ Use the `dk::usbd::ep0stall()` helper function to stall endpoint 0 in `nrf52-code/usb-app/src/bin/usb-4.rs` if an invalid request is received.
diff --git a/exercise-book/src/nrf52-usb-updating-device-state.md b/exercise-book/src/nrf52-usb-updating-device-state.md
index 38743e6..96f5dde 100644
--- a/exercise-book/src/nrf52-usb-updating-device-state.md
+++ b/exercise-book/src/nrf52-usb-updating-device-state.md
@@ -8,7 +8,7 @@ The device state should be tracked using a resource so that it's preserved acros
 
 ### Update the handling of the `USBRESET` event
 
-Instead of ignoring it, we now want it to change the state of the USB device. See section 9.1 USB Device States of the USB specification for details on what to do.
+Instead of ignoring it, we now want it to change the state of the USB device. See section 9.1 USB Device States of the USB specification for details on what to do. Note that `fn on_event()` was given `state: &mut State`.
 
 ### Update the handling of `SET_ADDRESS` requests