diff --git a/black.py b/black.py
index ce4a44f..61b884a 100644
--- a/black.py
+++ b/black.py
@@ -47,7 +47,7 @@
 __version__ = "18.5b1"
 DEFAULT_LINE_LENGTH = 88
 DEFAULT_EXCLUDES = (
-    r"build/|buck-out/|dist/|_build/|\.git/|\.hg/|\.mypy_cache/|\.tox/|\.venv/"
+    r"/(\.git|\.hg|\.mypy_cache|\.tox|\.venv|_build|buck-out|build|dist)/"
 )
 DEFAULT_INCLUDES = r"\.pyi?$"
 CACHE_DIR = Path(user_cache_dir("black", version=__version__))