diff --git a/src/ol/source/tilesource.js b/src/ol/source/tilesource.js
index 111fb6cf18..5bf8116f75 100644
--- a/src/ol/source/tilesource.js
+++ b/src/ol/source/tilesource.js
@@ -174,7 +174,7 @@ ol.source.Tile.prototype.getResolutions = function() {
  * @param {number} x Tile coordinate x.
  * @param {number} y Tile coordinate y.
  * @param {number} pixelRatio Pixel ratio.
- * @param {ol.proj.Projection=} opt_projection Projection.
+ * @param {ol.proj.Projection} projection Projection.
  * @return {!ol.Tile} Tile.
  */
 ol.source.Tile.prototype.getTile = goog.abstractMethod;