diff --git a/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb b/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
index ed9bfd83f..af72adc32 100644
--- a/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
+++ b/lib/redmine/wiki_formatting/common_mark/sanitization_filter.rb
@@ -78,7 +78,7 @@ module Redmine
 
             case node.name
             when 'div'
-              unless node['class'] =~ /\Amarkdown-alert markdown-alert-[a-z]+\z/
+              unless /\Amarkdown-alert markdown-alert-[a-z]+\z/.match?(node['class'])
                 node.remove_attribute('class')
               end
             when 'p'
diff --git a/test/unit/lib/redmine/wiki_formatting/common_mark/sanitization_filter_test.rb b/test/unit/lib/redmine/wiki_formatting/common_mark/sanitization_filter_test.rb
index a2902f4d9..b2d19eab9 100644
--- a/test/unit/lib/redmine/wiki_formatting/common_mark/sanitization_filter_test.rb
+++ b/test/unit/lib/redmine/wiki_formatting/common_mark/sanitization_filter_test.rb
@@ -51,7 +51,7 @@ if Object.const_defined?(:Commonmarker)
         %(<a href="#fn-1" id="fnref-1">foo</a>),
         %(<a href="#fn-1" id="fnref-1-2">foo</a>),
         %(<ol><li id="fn-1">footnote</li></ol>),
-      ].each do | input |
+      ].each do |input|
         assert_equal input, filter(input)
         assert_equal input, filter(input)
       end