diff --git a/src/control/Control.Layers.js b/src/control/Control.Layers.js
index 3d2ecb4c..df32c711 100644
--- a/src/control/Control.Layers.js
+++ b/src/control/Control.Layers.js
@@ -254,7 +254,7 @@ L.Control.Layers = L.Control.extend({
 	_expand: function () {
 		L.DomUtil.addClass(this._container, 'leaflet-control-layers-expanded');
 		this._form.style.height = null;
-		var acceptableHeight = this._map._size.y - (this._container.offsetTop + 50);
+		var acceptableHeight = this._map.getSize().y - (this._container.offsetTop + 50);
 		if (acceptableHeight < this._form.clientHeight) {
 			L.DomUtil.addClass(this._form, 'leaflet-control-layers-scrollbar');
 			this._form.style.height = acceptableHeight + 'px';