--- a/src/python_ast.rs
+++ b/src/python_ast.rs
@@ -9,10 +9,9 @@ pub struct Module {
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum stmt {
     // FunctionDef(identifier name, arguments args, stmt* body, expr* decorator_list, expr? returns)
-    FunctionDef(String, arguments, Vec<stmt>, Vec<expr>, Option<expr>),
-
     // AsyncFunctionDef(identifier name, arguments args, stmt* body, expr* decorator_list, expr? returns)
-    //AsyncFunctionDef(String/*, arguments, Vec<expr>),
+    // If the last field is true, then it's an AsyncFunctionDef.
+    FunctionDef(String, arguments, Vec<stmt>, Vec<expr>, Option<expr>, bool),
 
     // ClassDef(identifier name, expr* bases, keyword* keywords, stmt* body, expr* decorator_list)
     ClassDef(String, Vec<expr>, Vec<keyword>, Vec<stmt>, Vec<expr>),