diff --git a/mypy/test/config.py b/mypy/test/config.py
index 2dc4208b1e9d..2a1aa461bfdc 100644
--- a/mypy/test/config.py
+++ b/mypy/test/config.py
@@ -1,13 +1,13 @@
 from __future__ import annotations
 
 import os.path
+from pathlib import Path
 
 provided_prefix = os.getenv("MYPY_TEST_PREFIX", None)
 if provided_prefix:
     PREFIX = provided_prefix
 else:
-    this_file_dir = os.path.dirname(os.path.realpath(__file__))
-    PREFIX = os.path.dirname(os.path.dirname(this_file_dir))
+    PREFIX = str(Path(__file__).absolute().parent.parent.parent)
 
 # Location of test data files such as test case descriptions.
 test_data_prefix = os.path.join(PREFIX, "test-data", "unit")