diff --git a/cernservicexml/publisher.py b/cernservicexml/publisher.py
index 4e8a3b1..f2bc8e3 100644
--- a/cernservicexml/publisher.py
+++ b/cernservicexml/publisher.py
@@ -34,6 +34,7 @@
 
 import requests
 
+from ._compat import StringIO
 from .document import ServiceDocument
 
 
@@ -45,4 +46,5 @@ class XSLSPublisher(object):
     def send(cls, document, api_url='http://xsls.cern.ch'):
         """Send service document to XSLS."""
         assert isinstance(document, ServiceDocument)
-        return requests.post(api_url, data=document.to_xml())
+        return requests.post(api_url, files=dict(
+            file=StringIO(document.to_xml())))
diff --git a/tests/test_publisher.py b/tests/test_publisher.py
index f837a70..5edf9f0 100644
--- a/tests/test_publisher.py
+++ b/tests/test_publisher.py
@@ -13,6 +13,7 @@
 
 from datetime import datetime
 
+import cgi
 from cernservicexml import ServiceDocument, XSLSPublisher
 from cernservicexml._compat import import_httpretty
 
@@ -31,7 +32,15 @@ def test_xslspublisher_send():
     resp = XSLSPublisher.send(doc, api_url=EXAMPLE_URL)
     assert resp.status_code == 200
 
-    assert httpretty.last_request().body.decode('utf-8') == \
+    # Parse multipart/form-data (not supported by HTTPretty)
+    content_type = httpretty.last_request().headers['Content-Type'].split(';')
+    content_type = [x.strip() for x in content_type]
+    key, boundary = content_type[1].split("=")
+    data = cgi.parse_multipart(httpretty.last_request().rfile,
+                               {'boundary': boundary.encode('utf-8')})
+
+    assert 'file' in data
+    assert data['file'][0].decode('utf-8') == \
         '<serviceupdate xmlns="http://sls.cern.ch/SLS/XML/update">' \
         '<id>myid</id><availability>100</availability>' \
         '<timestamp>2015-01-01T00:00:00</timestamp></serviceupdate>'