diff --git a/orientation-sensor/resources/sensor-data.js b/orientation-sensor/resources/sensor-data.js
index d0b280fa6c4371..a2886e7553bd0e 100644
--- a/orientation-sensor/resources/sensor-data.js
+++ b/orientation-sensor/resources/sensor-data.js
@@ -15,9 +15,13 @@ const kRelativeOrientationSensorData = {
 };
 
 const kOrientationReadings = {
-  readings: [{quaternion: [1, 0, 0, 0]}],
-  expectedReadings: [{quaternion: [1, 0, 0, 0]}],
-  expectedRemappedReadings: [{quaternion: [-0.70710678, 0.70710678, 0, 0]}]
+  // WebDriver input data must be given in Euler angles according to
+  // https://w3c.github.io/deviceorientation/#parse-orientation-data-reading-algorithm
+  // and converted to quaternions via
+  // https://w3c.github.io/orientation-sensor/#create-a-quaternion-from-euler-angles.
+  readings: [{alpha: 0, beta: -180, gamma: 0}],
+  expectedReadings: [{quaternion: [-1, 0, 0, 0]}],
+  expectedRemappedReadings: [{quaternion: [0.70710678, -0.70710678, 0, 0]}]
 };
 
 const kRotationMatrix = [1,  0,  0, 0,