diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
index 0b3fea6b..e4ede026 100644
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -21,7 +21,7 @@ jobs:
         run: |
           pip install -r requirements/development.txt
           sudo apt-get -y update
-          sudo apt-get -y install graphviz libclang1-9 libclang-cpp9
+          sudo apt-get -y install graphviz libclang1-11 libclang-cpp11
 
       - name: install doxygen from SF binary archives
         env:
diff --git a/breathe/directives/__init__.py b/breathe/directives/__init__.py
index 9d9f5516..9988d610 100644
--- a/breathe/directives/__init__.py
+++ b/breathe/directives/__init__.py
@@ -24,7 +24,7 @@ def warn(
         self,
         raw_text: str,
         *,
-        rendered_nodes: Sequence[nodes.Node] = None,
+        rendered_nodes: Optional[Sequence[nodes.Node]] = None,
         unformatted_suffix: str = ""
     ) -> List[nodes.Node]:
         raw_text = self.format(raw_text) + unformatted_suffix
diff --git a/breathe/directives/content_block.py b/breathe/directives/content_block.py
index dfd6ec2e..bc3f560f 100644
--- a/breathe/directives/content_block.py
+++ b/breathe/directives/content_block.py
@@ -28,6 +28,7 @@ class _DoxygenContentBlockDirective(BaseDirective):
         "undoc-members": flag,
         "no-link": flag,
         "desc-only": flag,
+        "sort": flag,
     }
     has_content = False
 
diff --git a/breathe/file_state_cache.py b/breathe/file_state_cache.py
index 6d2d7193..da302606 100644
--- a/breathe/file_state_cache.py
+++ b/breathe/file_state_cache.py
@@ -49,7 +49,7 @@ def _get_outdated(
         return []
 
     stale = []
-    for filename, info in app.env.breathe_file_state.items():  # type: ignore
+    for filename, info in app.env.breathe_file_state.items():
         old_mtime, docnames = info
         if _getmtime(filename) > old_mtime:
             stale.extend(docnames)
@@ -61,14 +61,14 @@ def _purge_doc(app: Sphinx, env: BuildEnvironment, docname: str) -> None:
         return
 
     toremove = []
-    for filename, info in app.env.breathe_file_state.items():  # type: ignore
+    for filename, info in app.env.breathe_file_state.items():
         _, docnames = info
         docnames.discard(docname)
         if not docnames:
             toremove.append(filename)
 
     for filename in toremove:
-        del app.env.breathe_file_state[filename]  # type: ignore
+        del app.env.breathe_file_state[filename]
 
 
 def setup(app: Sphinx):
diff --git a/breathe/renderer/sphinxrenderer.py b/breathe/renderer/sphinxrenderer.py
index 1c9d28d0..dff0c982 100644
--- a/breathe/renderer/sphinxrenderer.py
+++ b/breathe/renderer/sphinxrenderer.py
@@ -649,10 +649,10 @@ def handle_declaration(
         node,
         declaration: str,
         *,
-        obj_type: str = None,
-        content_callback: ContentCallback = None,
-        display_obj_type: str = None,
-        declarator_callback: DeclaratorCallback = None,
+        obj_type: Optional[str] = None,
+        content_callback: Optional[ContentCallback] = None,
+        display_obj_type: Optional[str] = None,
+        declarator_callback: Optional[DeclaratorCallback] = None,
         options={},
     ) -> List[Node]:
         if obj_type is None:
@@ -1399,7 +1399,12 @@ def visit_sectiondef(self, node) -> List[Node]:
         node_list.extend(self.render_optional(node.description))
 
         # Get all the memberdef info
-        node_list.extend(self.render_iterable(node.memberdef))
+        if "sort" in options:
+            member_def = sorted(node.memberdef, key=lambda x: x.name)
+        else:
+            member_def = node.memberdef
+
+        node_list.extend(self.render_iterable(member_def))
 
         if node_list:
             if "members-only" in options: