diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index f617c2f3a00..d8798cf5beb 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -7,7 +7,8 @@ import os
 import sys
 import subprocess
 import tempfile
-from test.script_helper import spawn_python, kill_python, assert_python_ok, assert_python_failure
+from test.script_helper import (spawn_python, kill_python, assert_python_ok,
+    assert_python_failure)
 
 
 # XXX (ncoghlan): Move to script_helper and make consistent with run_python
@@ -370,6 +371,12 @@ class CmdLineTest(unittest.TestCase):
         assert_python_ok(filename)
 
 
+    def test_unknown_options(self):
+        rc, out, err = assert_python_failure('-z', __cleanenv=True)
+        self.assertIn(b'Unknown option', err)
+        self.assertEqual(err.splitlines().count(b'Unknown option: -z'), 1)
+        self.assertEqual(b'', out)
+
 def test_main():
     test.support.run_unittest(CmdLineTest)
     test.support.reap_children()
diff --git a/Misc/ACKS b/Misc/ACKS
index abf4a5ddc67..ced316890b1 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -835,6 +835,7 @@ Trent Nelson
 Chad Netzer
 Max Neunhöffer
 George Neville-Neil
+Hieu Nguyen
 Johannes Nicolai
 Samuel Nicolary
 Jonathan Niehof
diff --git a/Misc/NEWS b/Misc/NEWS
index 0cf165eb308..9771ecd5a36 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 3.3.1?
 Core and Builtins
 -----------------
 
+- Issue #16306: Fix multiple error messages when unknown command line
+  parameters where passed to the interpreter.  Patch by Hieu Nguyen.
+
 - Issue #16215: Fix potential double memory free in str.replace().  Patch
   by Serhiy Storchaka.
 
diff --git a/Python/getopt.c b/Python/getopt.c
index cc424312fe9..037aa5db51f 100644
--- a/Python/getopt.c
+++ b/Python/getopt.c
@@ -45,7 +45,7 @@ static wchar_t *opt_ptr = L"";
 
 void _PyOS_ResetGetOpt(void)
 {
-    _PyOS_opterr = 1;
+    _PyOS_opterr = 0;  /* prevent printing the error in 2nd loop in main.c */
     _PyOS_optind = 1;
     _PyOS_optarg = NULL;
     opt_ptr = L"";
@@ -90,18 +90,18 @@ int _PyOS_GetOpt(int argc, wchar_t **argv, wchar_t *optstring)
         opt_ptr = &argv[_PyOS_optind++][1];
     }
 
-    if ( (option = *opt_ptr++) == L'\0')
+    if ((option = *opt_ptr++) == L'\0')
         return -1;
 
     if (option == 'J') {
-        fprintf(stderr, "-J is reserved for Jython\n");
+        if (_PyOS_opterr)
+            fprintf(stderr, "-J is reserved for Jython\n");
         return '_';
     }
 
     if ((ptr = wcschr(optstring, option)) == NULL) {
         if (_PyOS_opterr)
-          fprintf(stderr, "Unknown option: -%c\n", (char)option);
-
+            fprintf(stderr, "Unknown option: -%c\n", (char)option);
         return '_';
     }