diff --git a/src/ol/source/imagearcgisrest.js b/src/ol/source/imagearcgisrest.js
index bfa75adfa3..b46ef2381e 100644
--- a/src/ol/source/imagearcgisrest.js
+++ b/src/ol/source/imagearcgisrest.js
@@ -208,7 +208,7 @@ ol.source.ImageArcGISRest.prototype.getRequestUrl_ = function(extent, size, pixe
   params['BBOX'] = extent.join(',');
   params['BBOXSR'] = srid;
   params['IMAGESR'] = srid;
-  params['DPI'] = 90 * pixelRatio;
+  params['DPI'] = Math.round(90 * pixelRatio);
 
   var url = this.url_;
 
diff --git a/test/spec/ol/source/imagearcgisrest.test.js b/test/spec/ol/source/imagearcgisrest.test.js
index 450f673e91..f1fe7672c0 100644
--- a/test/spec/ol/source/imagearcgisrest.test.js
+++ b/test/spec/ol/source/imagearcgisrest.test.js
@@ -38,10 +38,10 @@ describe('ol.source.ImageArcGISRest', function() {
 
     it('returns a non floating point DPI value', function() {
       var source = new ol.source.ImageArcGISRest(options);
-      var image = source.getImage([3, 2, -7, 1.12], resolution, pixelRatio, proj3857);
+      var image = source.getImage([3, 2, -7, 1.12], resolution, 1.01, proj3857);
       var uri = new URL(image.src_);
       var queryData = uri.searchParams;
-      expect(queryData.get('DPI')).to.be('90');
+      expect(queryData.get('DPI')).to.be('91');
     });
 
     it('returns a image with the expected URL for ImageServer', function() {