diff --git a/shotgun_api3/shotgun.py b/shotgun_api3/shotgun.py
index 7c968c4b8..9e05f2f91 100755
--- a/shotgun_api3/shotgun.py
+++ b/shotgun_api3/shotgun.py
@@ -2486,7 +2486,7 @@ def download_attachment(self, attachment=False, file_path=None, attachment_id=No
         try:
             request = urllib2.Request(url)
             request.add_header('user-agent', "; ".join(self._user_agents))
-            req = urllib2.urlopen(request)
+            req = urllib2.urlopen(request, cafile=os.environ.get('SHOTGUN_API_CACERTS', None))
             if file_path:
                 shutil.copyfileobj(req, fp)
             else: