diff --git a/docs/source/conf.py b/docs/source/conf.py
index d6b8bb0..2aaf14f 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -124,7 +124,7 @@ def setup(app):
     from better_toctree import TocTreeCollector
     app.add_env_collector(TocTreeCollector)
 
-    app.add_stylesheet('style.css')
+    app.add_css_file('style.css')
 
     from prettify_special_methods import PrettifySpecialMethods, show_special_methods
     app.add_transform(PrettifySpecialMethods)
diff --git a/docs/source/extensions/better_toctree.py b/docs/source/extensions/better_toctree.py
index a9804e2..53c221d 100644
--- a/docs/source/extensions/better_toctree.py
+++ b/docs/source/extensions/better_toctree.py
@@ -123,7 +123,7 @@ def build_toc(node, depth=1):
                         entries.append(onlynode)
                 # ADDED
                 elif isinstance(sectionnode, addnodes.desc):
-                    target = sectionnode.traverse(addnodes.desc_signature)[0]
+                    target = next(iter(sectionnode.traverse(addnodes.desc_signature)))
 
                     reference = nodes.reference(
                         '', '',
diff --git a/docs/source/extensions/strip_annotations.py b/docs/source/extensions/strip_annotations.py
index cdfeb2c..5333d0f 100644
--- a/docs/source/extensions/strip_annotations.py
+++ b/docs/source/extensions/strip_annotations.py
@@ -1,4 +1,4 @@
-from sphinx.util.inspect import Signature
+from sphinx.util.inspect import stringify_signature
 
 import inspect
 
@@ -18,14 +18,14 @@ def strip_annotations(
     if what not in {'function', 'method', 'class'}:
         return
 
-    new_signature = Signature(obj)
-    new_signature.signature = new_signature.signature.replace(
+    original_signature = inspect.signature(obj)
+    new_signature = original_signature.replace(
         return_annotation=inspect.Signature.empty,
         parameters=[
             param.replace(annotation=inspect.Parameter.empty)
-            for param in new_signature.signature.parameters.values()
+            for param in original_signature.parameters.values()
             if param.name != 'self'
         ],
     )
 
-    return new_signature.format_args(), None
+    return stringify_signature(new_signature), None
diff --git a/docs/source/mocks/sublime.py b/docs/source/mocks/sublime.py
index f448f13..7c97f9a 100644
--- a/docs/source/mocks/sublime.py
+++ b/docs/source/mocks/sublime.py
@@ -1,4 +1,4 @@
-from sphinx.ext.autodoc.importer import _MockObject
+from sphinx.ext.autodoc.mock import _MockObject
 
 import sys