diff --git a/src/tool/Tool.js b/src/tool/Tool.js
index 2fb27d90..6b924feb 100644
--- a/src/tool/Tool.js
+++ b/src/tool/Tool.js
@@ -295,6 +295,7 @@ var Tool = this.Tool = Base.extend({
 		}
 		// Make sure mousemove events have lastPoint set even for the first move
 		// so event.delta is always defined for them.
+		// TODO: Decide wether mousedown also should always have delta set.
 		this._lastPoint = start && type == 'mousemove' ? pt : this._point;
 		this._point = pt;
 		switch (type) {