nicholasserra · Nov 2, 2026 · Nov 1, 2026
diff --git a/CHANGES.md b/CHANGES.md
@@ -26,6 +26,7 @@
 - [pull #737] Fix XSS from code spans that the span gamut doesn't treat as code spans in safe mode (#726)
 - [pull #743] Add a `strip-syntax` option to the `header-ids` extra that leaves link URLs, image paths, inline HTML tags and emphasis markers out of header ids (#192)
 - [pull #747] Fix `link-patterns` extra linking text inside Markdown links and images whose label wraps onto another line
+- [pull #759] Fix `fenced-code-blocks` extra not recognizing code blocks whose language name contains `#` or `.`, such as `c#`, `f#` and `vb.net`
 
 
 ## python-markdown2 2.5.5

diff --git a/lib/markdown2.py b/lib/markdown2.py
@@ -3685,7 +3685,7 @@ class FencedCodeBlocks(Extra):
 
     fenced_code_block_re = re.compile(r'''
         (?:\n+|\A\n?|(?<=\n))
-        (^[ \t]*`{3,})\s{0,99}?([\w+-]+)?\s{0,99}?\n  # $1 = opening fence (captured for back-referencing), $2 = optional lang
+        (^[ \t]*`{3,})\s{0,99}?([\w+\#.-]+)?\s{0,99}?\n  # $1 = opening fence (captured for back-referencing), $2 = optional lang
         (.*?)                             # $3 = code block content
         \1[ \t]*\n                      # closing fence
         ''', re.M | re.X | re.S)

diff --git a/test/tm-cases/fenced_code_blocks_lang_with_symbols.html b/test/tm-cases/fenced_code_blocks_lang_with_symbols.html
@@ -0,0 +1,18 @@
+<div class="codehilite">
+<pre><span></span><code><span class="cp">#region Setup</span>
+<span class="kt">var</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
+<span class="cp">#endregion</span>
+</code></pre>
+</div>
+
+<p>Some <em>text</em> between the blocks.</p>
+
+<div class="codehilite">
+<pre><span></span><code><span class="k">let</span><span class="w"> </span><span class="nv">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span>
+</code></pre>
+</div>
+
+<div class="codehilite">
+<pre><span></span><code><span class="k">Dim</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="ow">As</span><span class="w"> </span><span class="kt">Integer</span>
+</code></pre>
+</div>
diff --git a/test/tm-cases/fenced_code_blocks_lang_with_symbols.opts b/test/tm-cases/fenced_code_blocks_lang_with_symbols.opts
@@ -0,0 +1 @@
+{"extras": ["fenced-code-blocks"]}
diff --git a/test/tm-cases/fenced_code_blocks_lang_with_symbols.tags b/test/tm-cases/fenced_code_blocks_lang_with_symbols.tags
@@ -0,0 +1 @@
+extra fenced-code-blocks pygments pygments>=2.21
diff --git a/test/tm-cases/fenced_code_blocks_lang_with_symbols.text b/test/tm-cases/fenced_code_blocks_lang_with_symbols.text
@@ -0,0 +1,15 @@
+```c#
+#region Setup
+var x = 1;
+#endregion
+```
+
+Some *text* between the blocks.
+
+```f#
+let x = 1
+```
+
+```vb.net
+Dim x As Integer
+```
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		extra fenced-code-blocks pygments pygments>=2.21