diff --git a/radicale/tests/test_base.py b/radicale/tests/test_base.py
index 381938f..e9360b5 100644
--- a/radicale/tests/test_base.py
+++ b/radicale/tests/test_base.py
@@ -770,6 +770,7 @@ class BaseRequestsMixIn:
         """Test if server sends authentication request."""
         self.configuration.set("auth", "type", "htpasswd")
         self.configuration.set("auth", "htpasswd_filename", os.devnull)
+        self.configuration.set("auth", "htpasswd_encryption", "plain")
         self.configuration.set("rights", "type", "owner_only")
         self.application = Application(self.configuration, self.logger)
         status, headers, answer = self.request("MKCOL", "/user/")