diff --git a/docs/changes.txt b/docs/changes.txt
index 2ab12cfa..83c536e1 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -4,6 +4,8 @@ WeeWX change history
 4.5.1 04/02/2021
 Reverted the wview schema back to the V3 style.
 
+setup.py keeps the OS environment when running wee_config as a subprocess.
+
 
 4.5.0 04/02/2021
 
diff --git a/setup.py b/setup.py
index 6c956d9e..ee433987 100755
--- a/setup.py
+++ b/setup.py
@@ -18,6 +18,7 @@ from __future__ import print_function
 from __future__ import with_statement
 
 import fnmatch
+import os
 import os.path
 import re
 import shutil
@@ -224,7 +225,7 @@ def find_files(directory, file_excludes=['*.pyc', "junk*"], dir_excludes=['*/__p
         # Find all the files in this directory
         for fn in os.listdir(d_path):
             filepath = os.path.join(d_path, fn)
-            # Make sure it's a file, and that it's name doesn't match the excluded pattern
+            # Make sure it's a file, and that its name doesn't match the excluded pattern
             if os.path.isfile(filepath) \
                     and not any(fnmatch.fnmatch(filepath, f) for f in file_excludes):
                 file_list.append(filepath)
@@ -276,8 +277,10 @@ def update_and_install_config(install_dir, install_scripts, install_lib, no_prom
     if DEBUG:
         log.info("Command used to invoke wee_config: %s" % args)
 
+    # Add the freshly installed WeeWX modules to PYTHONPATH, so wee_config can find them.
+    os.environ['PYTHONPATH'] = install_lib
+    # Run wee_config in a subprocess.
     proc = subprocess.Popen(args,
-                            env={'PYTHONPATH': install_lib},
                             stdin=sys.stdin,
                             stdout=sys.stdout,
                             stderr=sys.stderr)