diff --git a/src/ol/source/tiledwmssource.js b/src/ol/source/tiledwmssource.js
index de94ee02e0..8a9ae3e153 100644
--- a/src/ol/source/tiledwmssource.js
+++ b/src/ol/source/tiledwmssource.js
@@ -40,6 +40,13 @@ ol.source.TileWMS = function(options) {
    */
   this.params_ = options.params;
 
+  /**
+   * @private
+   * @type {string}
+   */
+  this.coordKeyPrefix_ = '';
+  this.resetCoordKeyPrefix_();
+
   if (goog.isDef(urls)) {
     var tileUrlFunctions = goog.array.map(
         urls, function(url) {
@@ -108,8 +115,7 @@ goog.inherits(ol.source.TileWMS, ol.source.TileImage);
  * @inheritDoc
  */
 ol.source.TileWMS.prototype.getKeyZXY = function(z, x, y) {
-  return goog.object.getValues(this.params_).join('/') +
-      goog.base(this, 'getKeyZXY', z, x, y);
+  return this.coordKeyPrefix_ + goog.base(this, 'getKeyZXY', z, x, y);
 };
 
 
@@ -146,11 +152,25 @@ ol.source.TileWMS.prototype.getFeatureInfoForPixel =
 };
 
 
+/**
+ * @private
+ */
+ol.source.TileWMS.prototype.resetCoordKeyPrefix_ = function() {
+  var i = 0;
+  var res = [];
+  for (var key in this.params_) {
+    res[i++] = key + '-' + this.params_[key];
+  }
+  this.coordKeyPrefix_ = res.join('/');
+};
+
+
 /**
  * Update the user-provided params.
  * @param {Object} params Params.
  */
 ol.source.TileWMS.prototype.updateParams = function(params) {
   goog.object.extend(this.params_, params);
+  this.resetCoordKeyPrefix_();
   this.dispatchChangeEvent();
 };
diff --git a/src/ol/source/wmtssource.js b/src/ol/source/wmtssource.js
index d65c6bdb4e..0a44eede2c 100644
--- a/src/ol/source/wmtssource.js
+++ b/src/ol/source/wmtssource.js
@@ -43,6 +43,13 @@ ol.source.WMTS = function(options) {
    */
   this.dimensions_ = options.dimensions || {};
 
+  /**
+   * @private
+   * @type {string}
+   */
+  this.coordKeyPrefix_ = '';
+  this.resetCoordKeyPrefix_();
+
   // FIXME: should we guess this requestEncoding from options.url(s)
   //        structure? that would mean KVP only if a template is not provided.
   var requestEncoding = goog.isDef(options.requestEncoding) ?
@@ -192,8 +199,20 @@ ol.source.WMTS.prototype.getDimensions = function() {
  * @inheritDoc
  */
 ol.source.WMTS.prototype.getKeyZXY = function(z, x, y) {
-  return goog.object.getValues(this.dimensions_).join('/') +
-      goog.base(this, 'getKeyZXY', z, x, y);
+  return this.coordKeyPrefix_ + goog.base(this, 'getKeyZXY', z, x, y);
+};
+
+
+/**
+ * @private
+ */
+ol.source.WMTS.prototype.resetCoordKeyPrefix_ = function() {
+  var i = 0;
+  var res = [];
+  for (var key in this.dimensions_) {
+    res[i++] = key + '-' + this.dimensions_[key];
+  }
+  this.coordKeyPrefix_ = res.join('/');
 };
 
 
@@ -203,6 +222,7 @@ ol.source.WMTS.prototype.getKeyZXY = function(z, x, y) {
  */
 ol.source.WMTS.prototype.updateDimensions = function(dimensions) {
   goog.object.extend(this.dimensions_, dimensions);
+  this.resetCoordKeyPrefix_();
   this.dispatchChangeEvent();
 };