diff --git a/lib/net/imap/response_reader.rb b/lib/net/imap/response_reader.rb
index 78930b01..139739d6 100644
--- a/lib/net/imap/response_reader.rb
+++ b/lib/net/imap/response_reader.rb
@@ -70,11 +70,10 @@ def min_response_remaining
         empty? ? 3 : done? ? 0 : (literal_size || 0) + 2
       end
 
-      def guard_response_too_large! = (raise self if response_too_large?)
-
-      def exception(msg = nil)
-        ResponseTooLargeError.new(
-          msg, max_response_size:, bytes_read:, literal_size:,
+      def guard_response_too_large!
+        return unless response_too_large?
+        raise ResponseTooLargeError.new(
+          max_response_size:, bytes_read:, literal_size:,
         )
       end
 
diff --git a/test/net/imap/fake_server/test_helper.rb b/test/net/imap/fake_server/test_helper.rb
index 8a91939e..0cc05907 100644
--- a/test/net/imap/fake_server/test_helper.rb
+++ b/test/net/imap/fake_server/test_helper.rb
@@ -16,6 +16,7 @@ module Net::IMAP::FakeServer::TestHelper
   def run_fake_server_in_thread(ignore_io_error: false,
                                 report_on_exception: true,
                                 timeout: 10, **opts)
+    timeout *= EnvUtil.timeout_scale || 1 if defined?(EnvUtil.timeout_scale)
     Timeout.timeout(timeout) do
       server = Net::IMAP::FakeServer.new(timeout: timeout, **opts)
       @threads << Thread.new do
diff --git a/test/net/imap/test_imap_max_response_size.rb b/test/net/imap/test_imap_max_response_size.rb
index ffb305b5..45aa1d95 100644
--- a/test/net/imap/test_imap_max_response_size.rb
+++ b/test/net/imap/test_imap_max_response_size.rb
@@ -36,6 +36,7 @@ class IMAPMaxResponseSizeTest < Net::IMAP::TestCase
     Net::IMAP.config.max_response_size = 1<<20
     with_fake_server(preauth: false, ignore_io_error: true) do |server, client|
       client.max_response_size = 50
+      client.noop # will reset response_reader, so the above config takes effect
       server.on("NOOP") do |resp|
         resp.untagged("1 FETCH (BODY[] {1000}\r\n" + "a" * 1000 + ")")
       end