diff --git a/bypy/linux/site.py b/bypy/linux/site.py
index 4e0dbf556b..396559b64a 100644
--- a/bypy/linux/site.py
+++ b/bypy/linux/site.py
@@ -8,6 +8,8 @@ import sys
 
 import _sitebuiltins
 
+USER_SITE = None
+
 
 def set_quit():
     eof = 'Ctrl-D (i.e. EOF)'
diff --git a/bypy/macos/site.py b/bypy/macos/site.py
index b490bb9fa5..90545770e9 100644
--- a/bypy/macos/site.py
+++ b/bypy/macos/site.py
@@ -3,6 +3,8 @@ import os
 import sys
 import _sitebuiltins
 
+USER_SITE = None
+
 
 def nuke_stdout():
     # Redirect stdout, stdin and stderr to /dev/null
diff --git a/bypy/windows/site.py b/bypy/windows/site.py
index 30775fe293..146027bcdf 100644
--- a/bypy/windows/site.py
+++ b/bypy/windows/site.py
@@ -13,6 +13,7 @@ import _sitebuiltins
 
 pyd_items = None
 extension_suffixes = sorted(EXTENSION_SUFFIXES, key=len, reverse=True)
+USER_SITE = None
 
 
 def remove_extension_suffix(name):