diff --git a/pydle/features/ircv3/sasl.py b/pydle/features/ircv3/sasl.py
index <HASH>..<HASH> 100644
--- a/pydle/features/ircv3/sasl.py
+++ b/pydle/features/ircv3/sasl.py
@@ -42,7 +42,7 @@ class SASLSupport(cap.CapabilityNegotiationSupport):
     def _sasl_start(self):
         """ Initiate SASL authentication. """
         # The rest will be handled in on_raw_authenticate()/_sasl_respond().
-        if not self._sasl_mechanisms or 'PLAIN' in self._sasl_mechanisms:
+        if not self._sasl_mechanisms or 'plain' in self._sasl_mechanisms:
             self.rawmsg('AUTHENTICATE', 'PLAIN')
             # Set a timeout handler.
             self._sasl_timer = self.eventloop.schedule_in(self.SASL_TIMEOUT, self._sasl_abort)
Using "plain" instead of "PLAIN" when checking for SASL mechs, since they're lowercased in features.ircv3.cap