diff --git a/src/ol/reproj/image.js b/src/ol/reproj/image.js
index 88c699a62a..0292d7168e 100644
--- a/src/ol/reproj/image.js
+++ b/src/ol/reproj/image.js
@@ -1,4 +1,5 @@
 goog.provide('ol.reproj.Image');
+goog.provide('ol.reproj.ImageFunctionType');
 
 goog.require('goog.asserts');
 goog.require('goog.events');
@@ -11,6 +12,12 @@ goog.require('ol.reproj');
 goog.require('ol.reproj.Triangulation');
 
 
+/**
+ * @typedef {function(ol.Extent, number, number) : ol.ImageBase}
+ */
+ol.reproj.ImageFunctionType;
+
+
 
 /**
  * @classdesc
@@ -24,7 +31,7 @@ goog.require('ol.reproj.Triangulation');
  * @param {ol.Extent} targetExtent Target extent.
  * @param {number} targetResolution Target resolution.
  * @param {number} pixelRatio Pixel ratio.
- * @param {function(ol.Extent, number, number):ol.ImageBase} getImageFunction
+ * @param {ol.reproj.ImageFunctionType} getImageFunction
  *     Function returning source images (extent, resolution, pixelRatio).
  */
 ol.reproj.Image = function(sourceProj, targetProj,
diff --git a/src/ol/reproj/tile.js b/src/ol/reproj/tile.js
index 7e5192e525..a1c819d620 100644
--- a/src/ol/reproj/tile.js
+++ b/src/ol/reproj/tile.js
@@ -1,4 +1,5 @@
 goog.provide('ol.reproj.Tile');
+goog.provide('ol.reproj.TileFunctionType');
 
 goog.require('goog.asserts');
 goog.require('goog.events');
@@ -14,6 +15,12 @@ goog.require('ol.reproj');
 goog.require('ol.reproj.Triangulation');
 
 
+/**
+ * @typedef {function(number, number, number, number) : ol.Tile}
+ */
+ol.reproj.TileFunctionType;
+
+
 
 /**
  * @classdesc
@@ -30,7 +37,7 @@ goog.require('ol.reproj.Triangulation');
  * @param {number} x X.
  * @param {number} y Y.
  * @param {number} pixelRatio Pixel ratio.
- * @param {function(number, number, number, number) : ol.Tile} getTileFunction
+ * @param {ol.reproj.TileFunctionType} getTileFunction
  *     Function returning source tiles (z, x, y, pixelRatio).
  * @param {number=} opt_errorThreshold Acceptable reprojection error (in px).
  * @param {boolean=} opt_renderEdges Render reprojection edges.