diff --git a/src/objectliterals.jsdoc b/src/objectliterals.jsdoc
index c2eb124ea1..60792392ac 100644
--- a/src/objectliterals.jsdoc
+++ b/src/objectliterals.jsdoc
@@ -236,8 +236,8 @@
  * @property {string|undefined} className CSS Class name. Default is `ol-scale-line`.
  * @property {number|undefined} minWidth Minimum width in pixels. Default is `64`.
  * @property {Element|undefined} target Target.
- * @property {ol.control.ScaleLineUnits|undefined} units Units.
- *     Default is `ol.control.ScaleLineUnits.METRIC`.
+ * @property {ol.control.ScaleLineUnits|string|undefined} units Units.
+ *     Default is `metric`.
  * @todo stability experimental
  */
 
diff --git a/src/ol/control/scalelinecontrol.js b/src/ol/control/scalelinecontrol.js
index 5c18bac16c..2aafe41044 100644
--- a/src/ol/control/scalelinecontrol.js
+++ b/src/ol/control/scalelinecontrol.js
@@ -122,7 +122,8 @@ ol.control.ScaleLine = function(opt_options) {
       this, ol.Object.getChangeEventType(ol.control.ScaleLineProperty.UNITS),
       this.handleUnitsChanged_, false, this);
 
-  this.setUnits(options.units || ol.control.ScaleLineUnits.METRIC);
+  this.setUnits(/** @type {ol.control.ScaleLineUnits} */ (options.units) ||
+      ol.control.ScaleLineUnits.METRIC);
 
 };
 goog.inherits(ol.control.ScaleLine, ol.control.Control);