diff -urNp -x '*.orig' Python-3.9.2.org/Lib/distutils/command/install.py Python-3.9.2/Lib/distutils/command/install.py
--- Python-3.9.2.org/Lib/distutils/command/install.py	2021-02-25 18:41:13.921266287 +0100
+++ Python-3.9.2/Lib/distutils/command/install.py	2021-02-25 18:41:15.634652993 +0100
@@ -9,6 +9,7 @@ from distutils import log
 from distutils.core import Command
 from distutils.debug import DEBUG
 from distutils.sysconfig import get_config_vars
+from distutils.sysconfig import PREFIX, EXEC_PREFIX
 from distutils.errors import DistutilsPlatformError
 from distutils.file_util import write_file
 from distutils.util import convert_path, subst_vars, change_root
@@ -419,8 +420,8 @@ class install(Command):
                     raise DistutilsOptionError(
                           "must not supply exec-prefix without prefix")
 
-                self.prefix = os.path.normpath(sys.prefix)
-                self.exec_prefix = os.path.normpath(sys.exec_prefix)
+                self.prefix = PREFIX
+                self.exec_prefix = EXEC_PREFIX
 
             else:
                 if self.exec_prefix is None:
diff -urNp -x '*.orig' Python-3.9.2.org/Lib/distutils/sysconfig.py Python-3.9.2/Lib/distutils/sysconfig.py
--- Python-3.9.2.org/Lib/distutils/sysconfig.py	2021-02-25 18:41:13.927933162 +0100
+++ Python-3.9.2/Lib/distutils/sysconfig.py	2021-02-25 18:41:15.634652993 +0100
@@ -19,6 +19,10 @@ from .errors import DistutilsPlatformErr
 # These are needed in a couple of spots, so just compute them once.
 PREFIX = os.path.normpath(sys.prefix)
 EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
+if PREFIX == "/usr":
+    PREFIX = "/usr/local"
+if EXEC_PREFIX == "/usr":
+    EXEC_PREFIX = "/usr/local"
 BASE_PREFIX = os.path.normpath(sys.base_prefix)
 BASE_EXEC_PREFIX = os.path.normpath(sys.base_exec_prefix)
 
diff -urNp -x '*.orig' Python-3.9.2.org/Lib/site.py Python-3.9.2/Lib/site.py
--- Python-3.9.2.org/Lib/site.py	2021-02-25 18:41:13.924599724 +0100
+++ Python-3.9.2/Lib/site.py	2021-02-25 18:41:15.634652993 +0100
@@ -76,7 +76,7 @@ import _sitebuiltins
 import io
 
 # Prefixes for site-packages; add additional prefixes like /usr/local here
-PREFIXES = [sys.prefix, sys.exec_prefix]
+PREFIXES = ["/usr/local", sys.prefix, sys.exec_prefix]
 # Enable per user site-packages directory
 # set it to False to disable the feature or True to force the feature
 ENABLE_USER_SITE = None