diff --git a/actionview/test/template/tag_helper_test.rb b/actionview/test/template/tag_helper_test.rb
index f401dfb699f..239309f7c7d 100644
--- a/actionview/test/template/tag_helper_test.rb
+++ b/actionview/test/template/tag_helper_test.rb
@@ -201,6 +201,8 @@ class TagHelperTest < ActionView::TestCase
                  content_tag(:p, "<script>evil_js</script>")
     assert_equal "<p><script>evil_js</script></p>",
                  content_tag(:p, "<script>evil_js</script>", nil, false)
+    assert_equal "<div @click=\"triggerNav()\">test</div>",
+                 content_tag(:div, "test", "@click": "triggerNav()")
   end
 
   def test_tag_builder_with_content
diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index d4ffff58965..597428ceeec 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -12,7 +12,7 @@ class ERB
     JSON_ESCAPE_REGEXP = /[\u2028\u2029&><]/u
 
     # Following XML requirements: https://www.w3.org/TR/REC-xml/#NT-Name
-    TAG_NAME_START_REGEXP_SET = ":A-Z_a-z\u{C0}-\u{D6}\u{D8}-\u{F6}\u{F8}-\u{2FF}\u{370}-\u{37D}\u{37F}-\u{1FFF}" \
+    TAG_NAME_START_REGEXP_SET = "@:A-Z_a-z\u{C0}-\u{D6}\u{D8}-\u{F6}\u{F8}-\u{2FF}\u{370}-\u{37D}\u{37F}-\u{1FFF}" \
                                 "\u{200C}-\u{200D}\u{2070}-\u{218F}\u{2C00}-\u{2FEF}\u{3001}-\u{D7FF}\u{F900}-\u{FDCF}" \
                                 "\u{FDF0}-\u{FFFD}\u{10000}-\u{EFFFF}"
     TAG_NAME_START_REGEXP = /[^#{TAG_NAME_START_REGEXP_SET}]/