diff --git a/lib/rdoc/markup/to_html.rb b/lib/rdoc/markup/to_html.rb
index 6477f98910..6baab3ff4e 100644
--- a/lib/rdoc/markup/to_html.rb
+++ b/lib/rdoc/markup/to_html.rb
@@ -300,9 +300,10 @@ def handle_TIDYLINK(label_part, url)
         if label_part.size == 1 && String === label_part[0]
           raw_label = label_part[0]
 
+          in_tidylink_label = @in_tidylink_label
           @in_tidylink_label = true
           special = apply_tidylink_label_special_handling(raw_label, url)
-          @in_tidylink_label = false
+          @in_tidylink_label = in_tidylink_label
 
           if special
             tag = gen_url(CGI.escapeHTML(url), special)
@@ -317,9 +318,10 @@ def handle_TIDYLINK(label_part, url)
         open_tag, close_tag = tag.split(/(?=<\/a>)/, 2)
         valid_tag = open_tag && close_tag
         emit_inline(open_tag) if valid_tag
+        in_tidylink_label = @in_tidylink_label
         @in_tidylink_label = true
         traverse_inline_nodes(label_part)
-        @in_tidylink_label = false
+        @in_tidylink_label = in_tidylink_label
         emit_inline(close_tag) if valid_tag
       end
 
@@ -544,7 +546,12 @@ def accept_heading(heading)
         if @pipe
           @res << to_html(heading.text)
         else
-          @res << "<a href=\"##{label}\">#{to_html(heading.text)}</a>"
+          # The heading text is the label of the heading's own link, so it must
+          # not contain links itself (nested <a> tags are invalid HTML).
+          @in_tidylink_label = true
+          text = to_html(heading.text)
+          @in_tidylink_label = false
+          @res << "<a href=\"##{label}\">#{text}</a>"
         end
 
         @res << "</h#{level}>\n"
diff --git a/test/rdoc/markup/to_html_crossref_test.rb b/test/rdoc/markup/to_html_crossref_test.rb
index 70242bb37f..83c0f56457 100644
--- a/test/rdoc/markup/to_html_crossref_test.rb
+++ b/test/rdoc/markup/to_html_crossref_test.rb
@@ -32,6 +32,21 @@ def test_convert_CROSSREF
     assert_equal para("<code># :stopdoc:</code>:"), result
   end
 
+  def test_convert_CROSSREF_in_heading
+    result = @to.convert "= C1 and EXAMPLE.md\n\nC1"
+
+    assert_equal "\n<span id=\"label-C1+and+EXAMPLE.md\" class=\"legacy-anchor\"></span>" \
+                 "\n<h1 id=\"c1-and-examplemd\"><a href=\"#c1-and-examplemd\">C1 and EXAMPLE.md</a></h1>\n" +
+                 para("<a href=\"C1.html\"><code>C1</code></a>"), result
+  end
+
+  def test_convert_CROSSREF_in_heading_after_tidylink
+    result = @to.convert "= {Foo}[https://example.com] C1"
+
+    assert_include result, '<a href="https://example.com">Foo</a>'
+    assert_not_include result, 'C1.html'
+  end
+
   def test_convert_CROSSREF_backslash_in_tt
     formatter = RDoc::Markup::ToHtmlCrossref.new('C9.html', @c9_b)