diff --git a/addons/share/res_users.py b/addons/share/res_users.py
index 9c9ae0034e2..56a3887b52a 100644
--- a/addons/share/res_users.py
+++ b/addons/share/res_users.py
@@ -33,7 +33,10 @@ class res_users(osv.osv):
 
     def _get_users_from_group(self, cr, uid, ids, context=None):
         result = set()
-        for group in self.pool['res.groups'].browse(cr, uid, ids, context=context):
+        groups = self.pool['res.groups'].browse(cr, uid, ids, context=context)
+        # Clear cache to avoid perf degradation on databases with thousands of users 
+        groups.invalidate_cache()
+        for group in groups:
             result.update(user.id for user in group.users)
         return list(result)