diff --git a/src/ol/source/imagewmssource.js b/src/ol/source/imagewmssource.js
index c950798036..44a5690deb 100644
--- a/src/ol/source/imagewmssource.js
+++ b/src/ol/source/imagewmssource.js
@@ -275,7 +275,7 @@ ol.source.ImageWMS.prototype.getRequestUrl_ = function(extent, size, pixelRatio,
   params[this.v13_ ? 'CRS' : 'SRS'] = projection.getCode();
 
   if (!('STYLES' in this.params_)) {
-    params['STYLES'] = new String('');
+    params['STYLES'] = '';
   }
 
   if (pixelRatio != 1) {
diff --git a/src/ol/source/tilewmssource.js b/src/ol/source/tilewmssource.js
index 6ed1864c59..4bdf2b2c63 100644
--- a/src/ol/source/tilewmssource.js
+++ b/src/ol/source/tilewmssource.js
@@ -234,7 +234,7 @@ ol.source.TileWMS.prototype.getRequestUrl_ = function(tileCoord, tileSize, tileE
   params[this.v13_ ? 'CRS' : 'SRS'] = projection.getCode();
 
   if (!('STYLES' in this.params_)) {
-    params['STYLES'] = new String('');
+    params['STYLES'] = '';
   }
 
   if (pixelRatio != 1) {
diff --git a/src/ol/xml.js b/src/ol/xml.js
index c4556fdf84..9d16765c52 100644
--- a/src/ol/xml.js
+++ b/src/ol/xml.js
@@ -64,9 +64,9 @@ ol.xml.getAllTextContent = function(node, normalizeWhitespace) {
  * @param {Node} node Node.
  * @param {boolean} normalizeWhitespace Normalize whitespace: remove all line
  * breaks.
- * @param {Array.<String|string>} accumulator Accumulator.
+ * @param {Array.<string>} accumulator Accumulator.
  * @private
- * @return {Array.<String|string>} Accumulator.
+ * @return {Array.<string>} Accumulator.
  */
 ol.xml.getAllTextContent_ = function(node, normalizeWhitespace, accumulator) {
   if (node.nodeType == goog.dom.NodeType.CDATA_SECTION ||