diff --git a/changelogs/unreleased/63417-add-missing-class.yml b/changelogs/unreleased/63417-add-missing-class.yml
new file mode 100644
index 00000000000..3030f5c57e4
--- /dev/null
+++ b/changelogs/unreleased/63417-add-missing-class.yml
@@ -0,0 +1,5 @@
+---
+title: Indent collapsible sections
+merge_request: 29804
+author:
+type: other
diff --git a/lib/gitlab/ci/ansi2html.rb b/lib/gitlab/ci/ansi2html.rb
index 6109b45ffd2..fc3223e7442 100644
--- a/lib/gitlab/ci/ansi2html.rb
+++ b/lib/gitlab/ci/ansi2html.rb
@@ -310,7 +310,7 @@ module Gitlab
 
           if @sections.any?
             css_classes << "section"
-            css_classes << "js-section-header" if @lineno_in_section == 0
+            css_classes << "js-section-header section-header" if @lineno_in_section == 0
             css_classes += sections.map { |section| "js-s-#{section}" }
           end
 
diff --git a/spec/lib/gitlab/ci/ansi2html_spec.rb b/spec/lib/gitlab/ci/ansi2html_spec.rb
index ac4612dda92..3d57ce431ab 100644
--- a/spec/lib/gitlab/ci/ansi2html_spec.rb
+++ b/spec/lib/gitlab/ci/ansi2html_spec.rb
@@ -231,8 +231,8 @@ describe Gitlab::Ci::Ansi2html do
 
       it 'prints light red' do
         text = "#{section_start}\e[91mHello\e[0m\n#{section_end}"
-        header = %{<span class="term-fg-l-red section js-section-header js-s-#{class_name(section_name)}">Hello</span>}
-        line_break = %{<span class="section js-section-header js-s-#{class_name(section_name)}"><br/></span>}
+        header = %{<span class="term-fg-l-red section js-section-header section-header js-s-#{class_name(section_name)}">Hello</span>}
+        line_break = %{<span class="section js-section-header section-header js-s-#{class_name(section_name)}"><br/></span>}
         line = %{<span class="section line s_#{class_name(section_name)}"></span>}
         empty_line = %{<span class="section js-s-#{class_name(section_name)}"></span>}
         html = "#{section_start_html}#{header}#{line_break}#{line}#{empty_line}#{section_end_html}"