diff --git a/python_app/tests/test_cart_firmware.py b/python_app/tests/test_cart_firmware.py
index 25f3af2..70fc807 100644
--- a/python_app/tests/test_cart_firmware.py
+++ b/python_app/tests/test_cart_firmware.py
@@ -7,6 +7,7 @@ import tempfile
 import unittest
 
 PROJECT = Path(__file__).resolve().parents[2]
+FIRMWARE = PROJECT / 'device_firmware/cart_firmware/src/main.cpp'
 
 ARDUINO_STUB = r'''
 #pragma once
@@ -46,14 +47,14 @@ inline void HAL_UART_Transmit(UART_HandleTypeDef*, uint8_t*, int, int) { ++trans
 
 
 @unittest.skipUnless(shutil.which('g++'), 'requires a host C++ compiler')
+@unittest.skipUnless(FIRMWARE.is_file(), 'firmware sources are not deployed to hosts')
 class CartFirmwareTest(unittest.TestCase):
     def test_schedule_rollover_and_sbus_encoding(self) -> None:
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)
             (root / 'Arduino.h').write_text(ARDUINO_STUB)
             source = root / 'check.cpp'
-            firmware = PROJECT / 'device_firmware/cart_firmware/src/main.cpp'
-            source.write_text(f'#include "{firmware}"\n' + r'''
+            source.write_text(f'#include "{FIRMWARE}"\n' + r'''
 #include <cassert>
 int main() {
     test_time = UINT32_MAX - 100;