diff --git a/pybricks/ev3devices.py b/pybricks/ev3devices.py
index ac0bffe..39b47cb 100644
--- a/pybricks/ev3devices.py
+++ b/pybricks/ev3devices.py
@@ -274,7 +274,7 @@ class UltrasonicSensor():
                            approximately 300 ms each time.
 
         Returns:
-            :ref:`distance`: Distance (millimeters).
+            :ref:`distance`: Distance.
 
         """
         pass