diff --git a/src/black/__init__.py b/src/black/__init__.py
index 380d48ed815..dc06eab8dd0 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -628,7 +628,7 @@ def get_sources(
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""
     sources: Set[Path] = set()
-    root: Path = ctx.obj["root"]
+    root = ctx.obj["root"]
 
     using_default_exclude = exclude is None
     exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES) if exclude is None else exclude