diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -84,24 +84,30 @@ def _write_atomic(path, data):
     """Best-effort function to write data to a path atomically.
     Be prepared to handle a FileExistsError if concurrent writing of the
     temporary file is attempted."""
-    if not sys.platform.startswith('win'):
+    if sys.platform.startswith('win'):
+        rename_to = None
+    else:
         # On POSIX-like platforms, renaming is atomic
-        path_tmp = path + '.tmp'
-        try:
-            fd = _os.open(path_tmp, _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY)
-            with _io.FileIO(fd, 'wb') as file:
-                file.write(data)
-            _os.rename(path_tmp, path)
-        except OSError:
-            try:
-                _os.unlink(path_tmp)
-            except OSError:
-                pass
-            raise
-    else:
-        with _io.FileIO(path, 'wb') as file:
+        rename_to = path
+
+    try:
+        _os.unlink(path)
+    except OSError:
+        pass
+
+    try:
+        flags = _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY | _os.O_TRUNC
+        fd = _os.open(path, flags)
+    except OSError:
+        return
+
+    try:
+        with _io.FileIO(fd, 'wb') as file:
             file.write(data)
-
+        if rename_to is not None:
+            _os.rename(path, rename_to)
+    except OSError:
+        _os.unlink(path)
 
 def _wrap(new, old):
     """Simple substitute for functools.wraps."""