diff --git a/README.md b/README.md
index dbb7922..540960e 100644
--- a/README.md
+++ b/README.md
@@ -577,7 +577,7 @@ to denote a significant space character.
 ```toml
 [tool.black]
 line-length = 88
-target_version = ['py37']
+target-version = ['py37']
 include = '\.pyi?$'
 exclude = '''
 
diff --git a/pyproject.toml b/pyproject.toml
index 3b192bf..d88fabe 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@
 
 [tool.black]
 line-length = 88
-target_version = ['py36', 'py37', 'py38']
+target-version = ['py36', 'py37', 'py38']
 include = '\.pyi?$'
 exclude = '''
 /(