diff --git a/scrapy/http/request/__init__.py b/scrapy/http/request/__init__.py
index d09eaf84..76a42819 100644
--- a/scrapy/http/request/__init__.py
+++ b/scrapy/http/request/__init__.py
@@ -66,7 +66,7 @@ class Request(object_ref):
         s = safe_url_string(url, self.encoding)
         self._url = escape_ajax(s)
 
-        if ':' not in self._url:
+        if ('://' not in self._url) and (not self._url.startswith('data:')):
             raise ValueError('Missing scheme in request url: %s' % self._url)
 
     url = property(_get_url, obsolete_setter(_set_url, 'url'))