diff --git a/lib/html/pipeline/sanitization_filter.rb b/lib/html/pipeline/sanitization_filter.rb
index 6d463e9f..0cb8fa21 100644
--- a/lib/html/pipeline/sanitization_filter.rb
+++ b/lib/html/pipeline/sanitization_filter.rb
@@ -33,7 +33,7 @@ class SanitizationFilter < Filter
       TABLE_SECTIONS = Set.new(%w[thead tbody tfoot].freeze)
 
       # These schemes are the only ones allowed in <a href> attributes by default.
-      ANCHOR_SCHEMES = ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac'].freeze
+      ANCHOR_SCHEMES = ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac', 'irc', 'ircs'].freeze
 
       # The main sanitization whitelist. Only these elements and attributes are
       # allowed through by default.
diff --git a/test/html/pipeline/sanitization_filter_test.rb b/test/html/pipeline/sanitization_filter_test.rb
index dbd53f70..6ef403f3 100644
--- a/test/html/pipeline/sanitization_filter_test.rb
+++ b/test/html/pipeline/sanitization_filter_test.rb
@@ -102,7 +102,7 @@ def test_uses_anchor_schemes_from_whitelist_when_not_separately_specified
   end
 
   def test_whitelist_contains_default_anchor_schemes
-    assert_equal SanitizationFilter::WHITELIST[:protocols]['a']['href'], ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac']
+    assert_equal SanitizationFilter::WHITELIST[:protocols]['a']['href'], ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac', 'irc', 'ircs']
   end
 
   def test_whitelist_from_full_constant
@@ -113,7 +113,7 @@ def test_whitelist_from_full_constant
   end
 
   def test_exports_default_anchor_schemes
-    assert_equal SanitizationFilter::ANCHOR_SCHEMES, ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac']
+    assert_equal SanitizationFilter::ANCHOR_SCHEMES, ['http', 'https', 'mailto', :relative, 'github-windows', 'github-mac', 'irc', 'ircs']
   end
 
   def test_script_contents_are_removed