diff --git a/pyproject.toml b/pyproject.toml
index 7795d0b..0c4646d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,3 @@
 [tool.black]
 line-length = 79
-target-version = ['py37']
+target-version = ['py39']