diff --git a/pyproject.toml b/pyproject.toml
index 8b3f572e7a842e3ce5d53fdbf36468f88d20db96..0a7432c5918c73dbed9a05e15a36e6cc30e18b4c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,7 +33,7 @@ build-backend = "setuptools.build_meta"
         showcontent = false
 
 [tool.black]
-target-version = ['py27']
+target-version = ['py39']
 extend-exclude = '''
 # A regex preceded with ^/ will apply only to files and directories
 # in the root of the project.