diff --git a/lib/net/ldap/connection.rb b/lib/net/ldap/connection.rb
index 4e3f6dd0..71ff7b43 100644
--- a/lib/net/ldap/connection.rb
+++ b/lib/net/ldap/connection.rb
@@ -130,7 +130,7 @@ def setup_encryption(args)
       if pdu.result_code.zero?
         @conn = self.class.wrap_with_ssl(@conn, args[:tls_options])
       else
-        raise Net::LDAP::StartTlSError, "start_tls failed: #{pdu.result_code}"
+        raise Net::LDAP::StartTLSError, "start_tls failed: #{pdu.result_code}"
       end
     else
       raise Net::LDAP::EncMethodUnsupportedError, "unsupported encryption method #{args[:method]}"