diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 00844bc..3c1abb7 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -261,9 +261,7 @@
         # 'inspect': 'i',
         # 'interactive': 'i',
         'dont_write_bytecode': 'B',
-        'no_user_site': 's',
         'no_site': 'S',
-        'ignore_environment': 'E',
         'verbose': 'v',
         'bytes_warning': 'b',
         'quiet': 'q',
@@ -275,6 +273,14 @@
         if v > 0:
             args.append('-' + opt * v)
 
+    if sys.flags.isolated:
+        args.append('-I')
+    else:
+        if sys.flags.ignore_environment:
+            args.append('-E')
+        if sys.flags.no_user_site:
+            args.append('-s')
+
     # -W options
     warnopts = sys.warnoptions[:]
     bytes_warning = sys.flags.bytes_warning