diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index 7d039ee00e6d25..d8f244353cd72a 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -7,7 +7,8 @@
 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
@@ -376,6 +377,12 @@ def test_del___main__(self):
         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 1095733839314e..1f51fbd551cd73 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -757,6 +757,7 @@ Tony Nelson
 Chad Netzer
 Max Neunhöffer
 George Neville-Neil
+Hieu Nguyen
 Johannes Nicolai
 Samuel Nicolary
 Gustavo Niemeyer
diff --git a/Misc/NEWS b/Misc/NEWS
index 3f2f7287befbce..c8580e33cb0ff3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.2.4
 Core and Builtins
 -----------------
 
+- Issue #16306: Fix multiple error messages when unknown command line
+  parameters where passed to the interpreter.  Patch by Hieu Nguyen.
+
 - Issue #16453: Fix equality testing of dead weakref objects.
 
 - Issue #9535: Fix pending signals that have been received but not yet
diff --git a/Python/getopt.c b/Python/getopt.c
index cc424312fe93c4..037aa5db51fb9a 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 '_';
     }