diff --git a/examples/js/controls/TrackballControls.js b/examples/js/controls/TrackballControls.js
index 78734eb348333b979f8732fcac42317db72797b5..d25416d4f78b9c85b27404797fec5934f87b1543 100644
--- a/examples/js/controls/TrackballControls.js
+++ b/examples/js/controls/TrackballControls.js
@@ -35,6 +35,8 @@ THREE.TrackballControls = function ( object, domElement ) {
 
 	this.keys = [ 65 /*A*/, 83 /*S*/, 68 /*D*/ ];
 
+	this.mouseButtons = { LEFT: THREE.MOUSE.LEFT, MIDDLE: THREE.MOUSE.MIDDLE, RIGHT: THREE.MOUSE.RIGHT };
+
 	// internals
 
 	this.target = new THREE.Vector3();
@@ -387,7 +389,24 @@ THREE.TrackballControls = function ( object, domElement ) {
 
 		if ( _state === STATE.NONE ) {
 
-			_state = event.button;
+			switch ( event.button ) {
+
+				case _this.mouseButtons.LEFT:
+					_state = STATE.ROTATE;
+					break;
+
+				case _this.mouseButtons.MIDDLE:
+					_state = STATE.ZOOM;
+					break;
+
+				case _this.mouseButtons.RIGHT:
+					_state = STATE.PAN;
+					break;
+
+				default:
+					_state = STATE.NONE;
+
+			}
 
 		}
 
diff --git a/examples/jsm/controls/TrackballControls.js b/examples/jsm/controls/TrackballControls.js
index a729c885344d4b3f2cedfba37bfdf88b2977f193..aaa41474ce5cc284bc018156fd1780b085db13c5 100644
--- a/examples/jsm/controls/TrackballControls.js
+++ b/examples/jsm/controls/TrackballControls.js
@@ -7,6 +7,7 @@
 
 import {
 	EventDispatcher,
+	MOUSE,
 	Quaternion,
 	Vector2,
 	Vector3
@@ -42,6 +43,8 @@ var TrackballControls = function ( object, domElement ) {
 
 	this.keys = [ 65 /*A*/, 83 /*S*/, 68 /*D*/ ];
 
+	this.mouseButtons = { LEFT: MOUSE.LEFT, MIDDLE: MOUSE.MIDDLE, RIGHT: MOUSE.RIGHT };
+
 	// internals
 
 	this.target = new Vector3();
@@ -394,7 +397,24 @@ var TrackballControls = function ( object, domElement ) {
 
 		if ( _state === STATE.NONE ) {
 
-			_state = event.button;
+			switch ( event.button ) {
+
+				case _this.mouseButtons.LEFT:
+					_state = STATE.ROTATE;
+					break;
+
+				case _this.mouseButtons.MIDDLE:
+					_state = STATE.ZOOM;
+					break;
+
+				case _this.mouseButtons.RIGHT:
+					_state = STATE.PAN;
+					break;
+
+				default:
+					_state = STATE.NONE;
+
+			}
 
 		}