diff --git a/setup.py b/setup.py
index 6b8231b..d461833 100644
--- a/setup.py
+++ b/setup.py
@@ -45,7 +45,10 @@ setup(
     include_package_data=True,
     install_requires=[
         'django-allauth',
-        'django-allauth-cas>=1.0.0b2,<1.1',
+        'django-allauth-cas>=1.0,<1.1',
+        # The version of CAS used by cas.eleves.ens.fr is unclear…
+        # Stick to python-cas 1.2.0 until we solve this mystery.
+        'python-cas==1.2.0',
         'django-widget-tweaks',
         'python-ldap',
     ],