diff --git a/stdlib/3/ast.pyi b/stdlib/3/ast.pyi
index c517aa6e2..7d58a80fd 100644
--- a/stdlib/3/ast.pyi
+++ b/stdlib/3/ast.pyi
@@ -49,6 +49,9 @@ else:
     @overload
     def parse(source: Union[str, bytes], filename: Union[str, bytes] = ..., mode: str = ...) -> AST: ...
 
+if sys.version_info >= (3, 9):
+    def unparse(ast_obj: AST) -> str: ...
+
 def copy_location(new_node: _T, old_node: AST) -> _T: ...
 def dump(node: AST, annotate_fields: bool = ..., include_attributes: bool = ...) -> str: ...
 def fix_missing_locations(node: _T) -> _T: ...