diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 8158bee302..6ad272697b 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -513,8 +513,6 @@ def check_options(self, args, func, expected=None):
         self.assertEqual(proc.stdout.rstrip(), repr(expected))
         self.assertEqual(proc.returncode, 0)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_args_from_interpreter_flags(self):
         # Test test.support.args_from_interpreter_flags()
         for opts in (
diff --git a/extra_tests/snippets/stdlib_sys.py b/extra_tests/snippets/stdlib_sys.py
index cb92fc6416..5d8859ac8e 100644
--- a/extra_tests/snippets/stdlib_sys.py
+++ b/extra_tests/snippets/stdlib_sys.py
@@ -1,4 +1,6 @@
 import sys
+import os
+import subprocess
 
 from testutils import assert_raises
 
@@ -105,4 +107,23 @@ def recursive_call(n):
     sys.set_int_max_str_digits(1)
 
 sys.set_int_max_str_digits(1000)
-assert sys.get_int_max_str_digits() == 1000
\ No newline at end of file
+assert sys.get_int_max_str_digits() == 1000
+
+# Test the PYTHONSAFEPATH environment variable
+code = "import sys; print(sys.flags.safe_path)"
+env = dict(os.environ)
+env.pop('PYTHONSAFEPATH', None)
+args = (sys.executable, '-P', '-c', code)
+
+proc = subprocess.run(
+    args, stdout=subprocess.PIPE,
+    universal_newlines=True, env=env)
+assert proc.stdout.rstrip() == 'True', proc
+assert proc.returncode == 0, proc
+
+env['PYTHONSAFEPATH'] = '1'
+proc = subprocess.run(
+    args, stdout=subprocess.PIPE,
+    universal_newlines=True, env=env)
+assert proc.stdout.rstrip() == 'True'
+assert proc.returncode == 0, proc
diff --git a/src/settings.rs b/src/settings.rs
index 6a47233353..494d594de4 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -100,6 +100,11 @@ fn parse_arguments<'a>(app: App<'a, '_>) -> ArgMatches<'a> {
                 .short("B")
                 .help("don't write .pyc files on import"),
         )
+        .arg(
+            Arg::with_name("safe-path")
+                .short("P")
+                .help("don’t prepend a potentially unsafe path to sys.path"),
+        )
         .arg(
             Arg::with_name("ignore-environment")
                 .short("E")
@@ -237,6 +242,12 @@ fn settings_from(matches: &ArgMatches) -> (Settings, RunMode) {
         };
     }
 
+    if matches.is_present("safe-path")
+        || (!ignore_environment && env::var_os("PYTHONSAFEPATH").is_some())
+    {
+        settings.safe_path = true;
+    }
+
     settings.check_hash_based_pycs = matches
         .value_of("check-hash-based-pycs")
         .unwrap_or("default")
diff --git a/vm/src/stdlib/sys.rs b/vm/src/stdlib/sys.rs
index 3a3824b310..47f9376f17 100644
--- a/vm/src/stdlib/sys.rs
+++ b/vm/src/stdlib/sys.rs
@@ -754,7 +754,7 @@ mod sys {
                 dev_mode: settings.dev_mode,
                 utf8_mode: settings.utf8_mode,
                 int_max_str_digits: settings.int_max_str_digits,
-                safe_path: false,
+                safe_path: settings.safe_path,
                 warn_default_encoding: settings.warn_default_encoding as u8,
             }
         }
diff --git a/vm/src/vm/setting.rs b/vm/src/vm/setting.rs
index 508c50da78..c4d1f85b2a 100644
--- a/vm/src/vm/setting.rs
+++ b/vm/src/vm/setting.rs
@@ -37,6 +37,9 @@ pub struct Settings {
     /// -B
     pub dont_write_bytecode: bool,
 
+    /// -P
+    pub safe_path: bool,
+
     /// -b
     pub bytes_warning: u64,
 
@@ -108,6 +111,7 @@ impl Default for Settings {
             verbose: 0,
             quiet: false,
             dont_write_bytecode: false,
+            safe_path: false,
             bytes_warning: 0,
             xopts: vec![],
             isolated: false,