Index: lib/redcloth3.rb
===================================================================
--- lib/redcloth3.rb	(revision 5097)
+++ lib/redcloth3.rb	(working copy)
@@ -707,11 +707,13 @@
             atts = pba( atts )
 
             # pass to prefix handler
+            replacement = nil
             if respond_to? "textile_#{ tag }", true
-                text.gsub!( $&, method( "textile_#{ tag }" ).call( tag, atts, cite, content ) )
+              replacement = method( "textile_#{ tag }" ).call( tag, atts, cite, content )
             elsif respond_to? "textile_#{ tagpre }_", true
-                text.gsub!( $&, method( "textile_#{ tagpre }_" ).call( tagpre, num, atts, cite, content ) )
+              replacement = method( "textile_#{ tagpre }_" ).call( tagpre, num, atts, cite, content )  
             end
+            text.gsub!( $& ) { replacement } if replacement
         end
     end
     
Index: test/unit/lib/redmine/wiki_formatting/textile_formatter_test.rb
===================================================================
--- test/unit/lib/redmine/wiki_formatting/textile_formatter_test.rb	(revision 5096)
+++ test/unit/lib/redmine/wiki_formatting/textile_formatter_test.rb	(working copy)
@@ -64,12 +64,18 @@
       '@<Location /redmine>@'    => '<code>&lt;Location /redmine&gt;</code>'
     )
   end
-  
+
   def test_escaping
     assert_html_output(
       'this is a <script>'      => 'this is a &lt;script&gt;'
     )
   end
+
+  def test_use_of_backslashes_followed_by_numbers_in_headers
+    assert_html_output({
+      'h1. 2009\02\09'      => '<h1>2009\02\09</h1>'
+    }, false)
+  end
   
   def test_double_dashes_should_not_strikethrough
     assert_html_output(
@@ -88,9 +94,9 @@
   
   private
   
-  def assert_html_output(to_test)
+  def assert_html_output(to_test, expect_paragraph = true)
     to_test.each do |text, expected|
-      assert_equal "<p>#{expected}</p>", @formatter.new(text).to_html, "Formatting the following text failed:\n===\n#{text}\n===\n"
+      assert_equal ( expect_paragraph ? "<p>#{expected}</p>" : expected ), @formatter.new(text).to_html, "Formatting the following text failed:\n===\n#{text}\n===\n"
     end
   end
 end