diff --git a/requirements.txt b/requirements.txt
index c1e07433ddb6af46064e882aad7a37fcd05b30ed..073564e311f0d41107cced6ce2288d19faab87f6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 # test_matchpy_interop.py
 matchpy
+astunparse; python_version < '3.9'