diff --git a/src/ol/source/wmssource.js b/src/ol/source/wmssource.js
index 23eec3dfa2..eebba21c2d 100644
--- a/src/ol/source/wmssource.js
+++ b/src/ol/source/wmssource.js
@@ -1,6 +1,7 @@
 goog.provide('ol.source.WMSGetFeatureInfoMethod');
 goog.provide('ol.source.wms');
 
+goog.require('goog.Uri');
 goog.require('goog.net.XhrIo');
 goog.require('goog.object');
 goog.require('goog.uri.utils');
@@ -102,7 +103,11 @@ ol.source.wms.getFeatureInfo =
     goog.object.extend(params, {'X': x, 'Y': y});
   }
   goog.object.extend(params, localOptions.params);
-  url = goog.uri.utils.appendParamsFromMap(url, params);
+  var uri = new goog.Uri(url, true);
+  for (var key in params) {
+    uri.setParameterValue(key, params[key]);
+  }
+  url = uri.toString();
   if (localOptions.method == ol.source.WMSGetFeatureInfoMethod.IFRAME) {
     goog.global.setTimeout(function() {
       success('<iframe seamless src="' + url + '"></iframe>');
diff --git a/test/spec/ol/source/wmssource.test.js b/test/spec/ol/source/wmssource.test.js
index fb23af0dbf..af0e6b7c58 100644
--- a/test/spec/ol/source/wmssource.test.js
+++ b/test/spec/ol/source/wmssource.test.js
@@ -32,8 +32,8 @@ describe('ol.source.wms', function() {
           [5, 10], {params: {'INFO_FORMAT': 'text/plain'}},
           function(info) {
             expect(info).to.eql('<iframe seamless src="' +
-                '?REQUEST=GetFeatureInfo&VERSION=1.3&LAYERS=foo&QUERY_LAYERS=' +
-                'foo&INFO_FORMAT=text%2Fplain&I=5&J=10"></iframe>');
+                '?request=GetFeatureInfo&version=1.3&layers=foo&query_layers=' +
+                'foo&info_format=text%2Fplain&i=5&j=10"></iframe>');
             done();
           });
     });
@@ -45,6 +45,17 @@ describe('ol.source.wms', function() {
             done();
           });
     });
+    it('overrides any existing parameters', function(done) {
+      ol.source.wms.getFeatureInfo('?REQUEST=GetMap&VERSION=1.3&LAYERS=' +
+          'foo&styles=x',
+          [5, 10], {params: {'INFO_FORMAT': 'text/plain', STYLES: 'y'}},
+          function(info) {
+            expect(info).to.eql('<iframe seamless src="' +
+                '?request=GetFeatureInfo&version=1.3&layers=foo&query_layers=' +
+                'foo&styles=y&info_format=text%2Fplain&i=5&j=10"></iframe>');
+            done();
+          });
+    });
   });
 
 });