diff --git a/src/usb/hid/ctap_hid.h b/src/usb/hid/ctap_hid.h
index 99af0ac..bc33e26 100644
--- a/src/usb/hid/ctap_hid.h
+++ b/src/usb/hid/ctap_hid.h
@@ -150,6 +150,8 @@ typedef struct {
 extern void add_keyboard_buffer(const uint8_t *, size_t, bool);
 extern void append_keyboard_buffer(const uint8_t *data, size_t data_len);
 
+extern uint16_t calculate_crc(const uint8_t *data, size_t data_len);
+
 #ifdef __cplusplus
 }
 #endif