diff --git a/.gitignore b/.gitignore
index 24c0e4318d..78d2adfe1c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,6 +11,8 @@
 /build/src
 /build/phantomjs-*-windows
 /build/phantomjs-*-windows.zip
+/build/proj4js-*.zip
+/build/proj4js
 /examples/*.json
 /examples/*.combined.js
 /examples/example-list.js
diff --git a/build.py b/build.py
index 6c09e4928b..e2c5264019 100755
--- a/build.py
+++ b/build.py
@@ -77,6 +77,10 @@ SRC = [path
 PLOVR_JAR = 'bin/plovr-eba786b34df9.jar'
 PLOVR_JAR_MD5 = '20eac8ccc4578676511cf7ccbfc65100'
 
+PROJ4JS = 'build/proj4js/lib/proj4js-combined.js'
+PROJ4JS_ZIP = 'build/proj4js-1.1.0.zip'
+PROJ4JS_ZIP_MD5 = '17caad64cf6ebc6e6fe62f292b134897'
+
 
 def report_sizes(t):
     t.info('uncompressed: %d bytes', os.stat(t.name).st_size)
@@ -338,8 +342,19 @@ def hostexamples(t):
     t.cp('examples/example-list.js', 'examples/example-list.xml', 'examples/Jugl.js', 'build/gh-pages/%(BRANCH)s/examples/')
 
 
+@target(PROJ4JS, PROJ4JS_ZIP)
+def proj4js(t):
+    from zipfile import ZipFile
+    ZipFile(PROJ4JS_ZIP).extractall('build')
+
+
+@target(PROJ4JS_ZIP, clean=False)
+def proj4js_zip(t):
+    t.download('http://download.osgeo.org/proj4js/' + os.path.basename(t.name), md5=PROJ4JS_ZIP_MD5)
+
+
 if sys.platform == 'win32':
-    @target('test', '%(PHANTOMJS)s', INTERNAL_SRC, 'test/requireall.js', phony=True)
+    @target('test', '%(PHANTOMJS)s', INTERNAL_SRC, PROJ4JS, 'test/requireall.js', phony=True)
     def test(t):
         t.run(PHANTOMJS, 'test/phantom-jasmine/run_jasmine_test.coffee', 'test/ol.html')
 
@@ -354,7 +369,7 @@ if sys.platform == 'win32':
         t.download('http://phantomjs.googlecode.com/files/' + os.path.basename(t.name))
 
 else:
-    @target('test', INTERNAL_SRC, 'test/requireall.js', phony=True)
+    @target('test', INTERNAL_SRC, PROJ4JS, 'test/requireall.js', phony=True)
     def test(t):
         t.run('%(PHANTOMJS)s', 'test/phantom-jasmine/run_jasmine_test.coffee', 'test/ol.html')
 
diff --git a/test/ol.html b/test/ol.html
index d4e3191ac9..979397f83e 100644
--- a/test/ol.html
+++ b/test/ol.html
@@ -25,6 +25,7 @@
   <script type="text/javascript" src="jasmine-1.2.0/jasmine-html.js"></script>
   <script type="text/javascript" src="phantom-jasmine/console-runner.js"></script>
   <script type="text/javascript" src="jasmine-extensions.js"></script>
+  <script type="text/javascript" src="../build/proj4js/lib/proj4js-combined.js"></script>
 
   <script type="text/javascript">
 
diff --git a/test/spec/ol/projection.test.js b/test/spec/ol/projection.test.js
index aeb881663a..eb1c9b4787 100644
--- a/test/spec/ol/projection.test.js
+++ b/test/spec/ol/projection.test.js
@@ -99,6 +99,33 @@ describe('ol.Projection', function() {
       expect(point.y).toRoughlyEqual(52.4827802220782, 1e-9);
     });
   });
+
+  describe('Proj4js integration', function() {
+
+    it('allows Proj4js projections to be used transparently', function() {
+      var point = ol.Projection.transformWithCodes(
+          new ol.Coordinate(-626172.13571216376, 6887893.4928337997),
+          'GOOGLE',
+          'WGS84');
+      expect(point.x).toRoughlyEqual(-5.625, 1e-9);
+      expect(point.y).toRoughlyEqual(52.4827802220782, 1e-9);
+    });
+
+    it('allows new Proj4js projections to be defined', function() {
+      Proj4js.defs['EPSG:21781'] =
+          '+proj=somerc +lat_0=46.95240555555556 +lon_0=7.439583333333333 ' +
+          '+k_0=1 +x_0=600000 +y_0=200000 +ellps=bessel ' +
+          '+towgs84=674.374,15.056,405.346,0,0,0,0 +units=m +no_defs';
+      var point = ol.Projection.transformWithCodes(
+          new ol.Coordinate(7.439583333333333, 46.95240555555556),
+          'EPSG:4326',
+          'EPSG:21781');
+      expect(point.x).toRoughlyEqual(600072.300, 1);
+      expect(point.y).toRoughlyEqual(200146.976, 1);
+    });
+
+  });
+
 });
 
 goog.require('goog.array');