1 files changed, 11 insertions, 0 deletions
diff --git a/sphinx/pycode/ast.py b/sphinx/pycode/ast.py
index 9bafff11c..0b403b61e 100644
--- a/sphinx/pycode/ast.py
+++ b/sphinx/pycode/ast.py
@@ -10,6 +10,7 @@
 
 import sys
 from typing import Dict, List, Type, Optional
+from typing import overload
 
 if sys.version_info > (3, 8):
     import ast
@@ -58,6 +59,16 @@ def parse(code: str, mode: str = 'exec') -> "ast.AST":
         return ast.parse(code, mode=mode)
 
 
+@overload
+def unparse(node: None) -> None:
+    ...
+
+
+@overload
+def unparse(node: ast.AST) -> str:
+    ...
+
+
 def unparse(node: Optional[ast.AST]) -> Optional[str]:
     """Unparse an AST to string."""
     if node is None: