diff --git a/spec/i18n_tasks_spec.rb b/spec/i18n_tasks_spec.rb
index 1f9f1803..e15b2525 100644
--- a/spec/i18n_tasks_spec.rb
+++ b/spec/i18n_tasks_spec.rb
@@ -14,22 +14,25 @@
       # These bin/i18n-tasks tests are executed in parallel for performance
       env = {'I18N_TASKS_BIN_SIMPLECOV_COVERAGE' => '1'}
       in_test_app_dir do
-        clean_parser_warning = -> s { s.sub %r(\Awarning: parser/current.*?https://github.com/whitequark/parser#compatibility-with-ruby-mri.\n)m, '' }
+        clean_unrelated_warnings = -> s {
+          s.sub(%r(^warning: parser/cur.*?https://github.com/whitequark/parser#compatibility-with-ruby-mri\.\n)m, '')
+              .gsub(/^.*warning: constant ::(?:Fixnum|Bignum) is deprecated\n/, '')
+        }
         clean_coverage_logging = -> s { s.sub /(?:\n^|\A)(?:Coverage = |.*Reporting coverage).*(?:$\n|\z)/i, '' }
         [
             proc {
               out, err, status = Open3.capture3(env, 'bundle exec ../../bin/i18n-tasks')
-              out, err = clean_coverage_logging[out], clean_parser_warning[clean_coverage_logging[err]]
+              out, err = clean_coverage_logging[out], clean_unrelated_warnings[clean_coverage_logging[err]]
               expect(status).to be_success
               expect(out).to be_empty
-              expect(err).to start_with('Usage: i18n-tasks [command] [options]')
+              expect(err.lines.first.chomp).to eq('Usage: i18n-tasks [command] [options]')
               expect(err).to include('Available commands', 'add-missing')
               # a task from a plugin
               expect(err).to include('greet')
             },
             proc {
               out, err, status = Open3.capture3(env, 'bundle exec ../../bin/i18n-tasks --version')
-              out, err = clean_coverage_logging[out], clean_parser_warning[clean_coverage_logging[err]]
+              out, err = clean_coverage_logging[out], clean_unrelated_warnings[clean_coverage_logging[err]]
               expect(status).to be_success
               expect(err).to be_empty
               expect(out.chomp).to eq I18n::Tasks::VERSION