diff --git a/marko/ext/toc.py b/marko/ext/toc.py
index c4a40a6..5bfc026 100644
--- a/marko/ext/toc.py
+++ b/marko/ext/toc.py
@@ -25,11 +25,16 @@
 
 import re
 
-from slugify import slugify
-
 from marko.helpers import MarkoExtension, render_dispatch  # type: ignore
 from marko.html_renderer import HTMLRenderer
 
+try:
+    from slugify import slugify
+except ImportError:
+
+    def slugify(source: str) -> str:  # type: ignore[misc]
+        return re.sub(r"[^\w\- ]+", "", source).strip().lower().replace(" ", "-")
+
 
 class TocRendererMixin:
     opening = "<ul>"
@@ -71,7 +76,8 @@ def render_toc(self, maxdepth=3):
     @render_dispatch(HTMLRenderer)
     def render_heading(self, element):
         children = self.render_children(element)
-        slug = slugify(re.sub(r"<.+?>", "", children))
+        raw = re.sub(r"<.+?>", "", children)
+        slug = slugify(raw)
         self.headings.append((int(element.level), slug, children))
         return '<h{0} id="{1}">{2}</h{0}>\n'.format(element.level, slug, children)