diff --git a/news/81.bugfix b/news/81.bugfix
new file mode 100644
index 0000000000000000000000000000000000000000..f994c546f26091fa4143a44d1c3b117f88120f7d
--- /dev/null
+++ b/news/81.bugfix
@@ -0,0 +1 @@
+Fix wheel builds when `package_dir` is mapped.
diff --git a/news/81.feature b/news/81.feature
new file mode 100644
index 0000000000000000000000000000000000000000..9d62f484d8824a39ab7f22ce98465a090ebd2eab
--- /dev/null
+++ b/news/81.feature
@@ -0,0 +1 @@
+Add test cases for `pdm build`.
diff --git a/tests/conftest.py b/tests/conftest.py
index 1b1d9aaf665a3c83e7c4993a2fb3940e2466cc9c..ea3078a245c5373cbcee81827d156f60c70a90d1 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -4,6 +4,7 @@ import json
 import os
 import shutil
 import sys
+from distutils.dir_util import copy_tree
 from io import BytesIO
 from pathlib import Path
 from typing import Callable, Iterable, List, Optional, Tuple
@@ -265,7 +266,7 @@ def fixture_project(project_no_init):
 
     def func(project_name):
         source = FIXTURES / "projects" / project_name
-        shutil.copytree(source, project_no_init.root, dirs_exist_ok=True)
+        copy_tree(source.as_posix(), project_no_init.root.as_posix())
         return project_no_init
 
     return func