Issue #24688: ast.get_docstring() for 'async def' functions.
diff --git a/Lib/ast.py b/Lib/ast.py
index 02c3b28..03c30f6 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -194,7 +194,7 @@
     be found.  If the node provided does not have docstrings a TypeError
     will be raised.
     """
-    if not isinstance(node, (FunctionDef, ClassDef, Module)):
+    if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):
         raise TypeError("%r can't have docstrings" % node.__class__.__name__)
     if node.body and isinstance(node.body[0], Expr) and \
        isinstance(node.body[0].value, Str):