diff --git a/src/ol/proj/epsg4326.js b/src/ol/proj/epsg4326.js
index f1d45aa13b..02e4d4ee31 100644
--- a/src/ol/proj/epsg4326.js
+++ b/src/ol/proj/epsg4326.js
@@ -67,4 +67,5 @@ export const PROJECTIONS = [
   new EPSG4326Projection('urn:ogc:def:crs:OGC:2:84'),
   new EPSG4326Projection('http://www.opengis.net/gml/srs/epsg.xml#4326', 'neu'),
   new EPSG4326Projection('urn:x-ogc:def:crs:EPSG:4326', 'neu'),
+  new EPSG4326Projection('urn:x-ogc:def:crs:EPSG:6.6:4326', 'neu'),
 ];
diff --git a/test/spec/ol/proj.test.js b/test/spec/ol/proj.test.js
index be4cd588e9..1a77c33894 100644
--- a/test/spec/ol/proj.test.js
+++ b/test/spec/ol/proj.test.js
@@ -215,12 +215,13 @@ describe('ol.proj', function () {
     });
 
     it(
-      'gives that CRS:84, urn:ogc:def:crs:EPSG:6.6:4326, EPSG:4326 are ' +
-        'equivalent',
+      'gives that CRS:84, urn:ogc:def:crs:EPSG:6.6:4326, EPSG:4326, ' +
+        'urn:x-ogc:def:crs:EPSG:6.6:4326 are equivalent',
       function () {
         _testAllEquivalent([
           'CRS:84',
           'urn:ogc:def:crs:EPSG:6.6:4326',
+          'urn:x-ogc:def:crs:EPSG:6.6:4326',
           'EPSG:4326',
         ]);
       }