Closes #14768: os.path.expanduser('~/a') doesn't works correctly when HOME is '/'
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index 8bb78d6..957a903 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -201,6 +201,7 @@
             with test_support.EnvironmentVarGuard() as env:
                 env['HOME'] = '/'
                 self.assertEqual(posixpath.expanduser("~"), "/")
+                self.assertEqual(posixpath.expanduser("~/foo"), "/foo")
 
     def test_normpath(self):
         self.assertEqual(posixpath.normpath(""), ".")