diff --git a/src/ol/geom/linestring.js b/src/ol/geom/linestring.js
index 0d80bca4f1..3477285f3c 100644
--- a/src/ol/geom/linestring.js
+++ b/src/ol/geom/linestring.js
@@ -117,7 +117,7 @@ ol.geom.LineString.prototype.closestPointXY =
  * return the last coordinate.
  *
  * @param {number} m M.
- * @param {boolean=} opt_extrapolate Extrapolate.
+ * @param {boolean=} opt_extrapolate Extrapolate. Default is `false`.
  * @return {ol.Coordinate} Coordinate.
  * @api stable
  */
diff --git a/src/ol/geom/multilinestring.js b/src/ol/geom/multilinestring.js
index 751636a8b9..b419475733 100644
--- a/src/ol/geom/multilinestring.js
+++ b/src/ol/geom/multilinestring.js
@@ -121,8 +121,8 @@ ol.geom.MultiLineString.prototype.closestPointXY =
  * LineStrings.
  *
  * @param {number} m M.
- * @param {boolean=} opt_extrapolate Extrapolate.
- * @param {boolean=} opt_interpolate Interpolate.
+ * @param {boolean=} opt_extrapolate Extrapolate. Default is `false`.
+ * @param {boolean=} opt_interpolate Interpolate. Default is `false`.
  * @return {ol.Coordinate} Coordinate.
  * @api stable
  */