diff --git a/pelican/contents.py b/pelican/contents.py
index d56335dd..ed213c31 100644
--- a/pelican/contents.py
+++ b/pelican/contents.py
@@ -141,14 +141,21 @@ class Content(object):
         """Returns the URL, formatted with the proper values"""
         metadata = copy.copy(self.metadata)
         path = self.metadata.get('path', self.get_relative_source_path())
+        default_category = self.settings['DEFAULT_CATEGORY']
+        slug_substitutions = self.settings.get('SLUG_SUBSTITUTIONS', ())
         metadata.update({
             'path': path_to_url(path),
             'slug': getattr(self, 'slug', ''),
             'lang': getattr(self, 'lang', 'en'),
             'date': getattr(self, 'date', datetime.now()),
-            'author': getattr(self, 'author', ''),
-            'category': getattr(self, 'category',
-                                self.settings['DEFAULT_CATEGORY']),
+            'author': slugify(
+                getattr(self, 'author', ''),
+                slug_substitutions
+            ),
+            'category': slugify(
+                getattr(self, 'category', default_category),
+                slug_substitutions
+            )
         })
         return metadata
 
diff --git a/pelican/tests/test_contents.py b/pelican/tests/test_contents.py
index c081639d..af97db3f 100644
--- a/pelican/tests/test_contents.py
+++ b/pelican/tests/test_contents.py
@@ -191,6 +191,20 @@ class TestArticle(TestPage):
         custom_article = Article(**article_kwargs)
         self.assertEqual('custom', custom_article.template)
 
+    def test_slugify_category_author(self):
+        settings = get_settings()
+        settings['SLUG_SUBSTITUTIONS'] = [ ('C#', 'csharp') ]
+        settings['ARTICLE_URL'] = '{author}/{category}/{slug}/'
+        settings['ARTICLE_SAVE_AS'] = '{author}/{category}/{slug}/index.html'
+        article_kwargs = self._copy_page_kwargs()
+        article_kwargs['metadata']['author'] = "O'Brien"
+        article_kwargs['metadata']['category'] = 'C# & stuff'
+        article_kwargs['metadata']['title'] = 'fnord'
+        article_kwargs['settings'] = settings
+        article = Article(**article_kwargs)
+        self.assertEqual(article.url, 'obrien/csharp-stuff/fnord/')
+        self.assertEqual(article.save_as, 'obrien/csharp-stuff/fnord/index.html')
+
 
 class TestURLWrapper(unittest.TestCase):
     def test_comparisons(self):