diff --git a/setup.py b/setup.py
index f33792e..b52f1c1 100644
--- a/setup.py
+++ b/setup.py
@@ -79,7 +79,7 @@ def readfile(path):
     ],
     'package_dir': {'': '.'},
     'install_requires': [
-        'repoze.sendmail',
+        'repoze.sendmail == 4.1',
         'requests',
     ],
     'entry_points': {