diff --git a/src/all.js b/src/all.js
index 4acf926f1f..54f9026c22 100644
--- a/src/all.js
+++ b/src/all.js
@@ -12,3 +12,4 @@ goog.require('ol.TileBounds');
 goog.require('ol.TileCoord');
 goog.require('ol.TileGrid');
 goog.require('ol.TileUrl');
+goog.require('ol.TransformFunction');
diff --git a/src/ol/projection.js b/src/ol/projection.js
index 177d584f22..4a9f08d7ff 100644
--- a/src/ol/projection.js
+++ b/src/ol/projection.js
@@ -5,12 +5,7 @@ goog.require('goog.asserts');
 goog.require('goog.math.Coordinate');
 goog.require('goog.object');
 goog.require('ol.Extent');
-
-
-/**
- * @typedef {function(goog.math.Coordinate): goog.math.Coordinate}
- */
-ol.TransformFunction;
+goog.require('ol.TransformFunction');
 
 
 /**
diff --git a/src/ol/transformfunction.js b/src/ol/transformfunction.js
new file mode 100644
index 0000000000..2f2f2ed532
--- /dev/null
+++ b/src/ol/transformfunction.js
@@ -0,0 +1,9 @@
+goog.provide('ol.TransformFunction');
+
+goog.require('goog.math.Coordinate');
+
+
+/**
+ * @typedef {function(goog.math.Coordinate): goog.math.Coordinate}
+ */
+ol.TransformFunction;