diff --git a/setuptools/wheel.py b/setuptools/wheel.py
index 4a33b20324..7d79fae278 100644
--- a/setuptools/wheel.py
+++ b/setuptools/wheel.py
@@ -37,6 +37,8 @@ def unpack(src_dir, dst_dir):
         for f in filenames:
             src = os.path.join(dirpath, f)
             dst = os.path.join(dst_dir, subdir, f)
+            if os.path.exists(dst):
+                os.remove(dst)
             os.renames(src, dst)
         for n, d in reversed(list(enumerate(dirnames))):
             src = os.path.join(dirpath, d)