diff --git a/firmware/xiao-esp32c6-sensor-node/imu.cpp b/firmware/xiao-esp32c6-sensor-node/imu.cpp
index 66f8819..16e0f54 100644
--- a/firmware/xiao-esp32c6-sensor-node/imu.cpp
+++ b/firmware/xiao-esp32c6-sensor-node/imu.cpp
@@ -8,16 +8,16 @@ namespace {
 Adafruit_BNO08x bno086(-1);
 sh2_SensorValue_t value;
 bool initialized = false;
-float degrees(float r) { return r * 180.0f / PI; }
+float radiansToDegrees(float r) { return r * 180.0f / PI; }
 void updateEuler(ImuState& s) {
     float sinr = 2 * (s.real * s.i + s.j * s.k);
     float cosr = 1 - 2 * (s.i * s.i + s.j * s.j);
-    s.rollDegrees = degrees(atan2f(sinr, cosr));
+    s.rollDegrees = radiansToDegrees(atan2f(sinr, cosr));
     float sinp = 2 * (s.real * s.j - s.k * s.i);
-    s.pitchDegrees = degrees(fabsf(sinp) >= 1 ? copysignf(PI / 2, sinp) : asinf(sinp));
+    s.pitchDegrees = radiansToDegrees(fabsf(sinp) >= 1 ? copysignf(PI / 2, sinp) : asinf(sinp));
     float siny = 2 * (s.real * s.k + s.i * s.j);
     float cosy = 1 - 2 * (s.j * s.j + s.k * s.k);
-    s.yawDegrees = degrees(atan2f(siny, cosy));
+    s.yawDegrees = radiansToDegrees(atan2f(siny, cosy));
 }
 }
 
@@ -36,4 +36,3 @@ void updateImu(ImuState& s) {
     s.accuracy = value.status; s.valid = true; s.lastUpdateMs = millis();
     updateEuler(s);
 }
-
diff --git a/tests/test_xiao_sensor_node_contract.py b/tests/test_xiao_sensor_node_contract.py
index 671eb32..a0ea602 100644
--- a/tests/test_xiao_sensor_node_contract.py
+++ b/tests/test_xiao_sensor_node_contract.py
@@ -21,7 +21,11 @@ def test_loop_is_non_blocking():
     assert "updateGps" in loop and "updateImu" in loop and "TELEMETRY_INTERVAL_MS" in loop
     assert not re.search(r"delay\((?:[2-9]|[1-9]\d+)\)", loop)
 
+def test_imu_does_not_redeclare_arduino_degrees_macro():
+    imu = source("imu.cpp")
+    assert "float degrees(" not in imu
+    assert "radiansToDegrees" in imu
+
 def test_node_does_not_take_cargo_or_ble_authority():
     combined = "\n".join(p.read_text() for p in NODE.glob("*.*"))
     assert "NimBLE" not in combined and "JBD" not in combined and "server.on(" not in combined
-