diff -r fb70ea8b7b2d Lib/test/test_urlparse.py
--- a/Lib/test/test_urlparse.py	Tue Apr 26 09:31:11 2016 +0300
+++ b/Lib/test/test_urlparse.py	Tue Apr 26 14:48:15 2016 +0300
@@ -748,7 +748,6 @@ class UrlParseTestCase(unittest.TestCase
                 self.assertEqual(func(b"path", scheme=b"ftp").scheme, b"ftp")
                 self.assertEqual(func("path").scheme, "")
                 self.assertEqual(func(b"path").scheme, b"")
-                self.assertEqual(func(b"path", "").scheme, b"")
 
     def test_parse_fragments(self):
         # Exercise the allow_fragments parameter of urlparse() and urlsplit()
@@ -800,6 +799,113 @@ class UrlParseTestCase(unittest.TestCase
         with self.assertRaisesRegex(TypeError, "Cannot mix str"):
             urllib.parse.urljoin(b"http://python.org", "http://python.org")
 
+    def test_false_args(self):
+        from urllib.parse import (urlparse, urlsplit, urlunparse, urlunsplit,
+                                  urljoin, urldefrag, parse_qsl)
+
+        self.assertRaises(TypeError, urlparse, None)
+        self.assertWarns(DeprecationWarning, urlparse, ())
+        self.assertWarns(DeprecationWarning, urlparse, b'www.python.org', '')
+        self.assertWarns(DeprecationWarning, urlparse, 'www.python.org', b'')
+
+        self.assertRaises(TypeError, urlsplit, None)
+        self.assertWarns(DeprecationWarning, urlsplit, ())
+        self.assertWarns(DeprecationWarning, urlsplit, b'www.python.org', '')
+        self.assertWarns(DeprecationWarning, urlsplit, 'www.python.org', b'')
+
+        with self.assertRaises(TypeError):
+            urlunparse((b"", "www.python.org", "", "", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunparse((None, "www.python.org", "", "", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", b"", "", "", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", None, "", "", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunparse(("http", "www.python.org", b"", "", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunparse(("http", "www.python.org", None, "", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", b"", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", None, "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", "", b"", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", "", None, ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", "", "", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse(("http", "www.python.org", "", "", "", None))
+        with self.assertRaises(TypeError):
+            urlunparse(("", b"www.python.org", b"", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((None, b"www.python.org", b"", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", "", b"", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", None, b"", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", "", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", None, b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", "", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", None, b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", b"", "", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", b"", None, b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", b"", b"", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunparse((b"http", b"www.python.org", b"", b"", b"", None))
+
+        with self.assertRaises(TypeError):
+            urlunsplit((b"", "www.python.org", "", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunsplit((None, "www.python.org", "", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", b"", "", "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", None, "", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunsplit(("http", "www.python.org", b"", "", ""))
+        with self.assertWarns(DeprecationWarning), self.assertRaises(TypeError):
+            urlunsplit(("http", "www.python.org", None, "", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", "www.python.org", "", b"", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", "www.python.org", "", None, ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", "www.python.org", "", "", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit(("http", "www.python.org", "", "", None))
+        with self.assertRaises(TypeError):
+            urlunsplit(("", b"www.python.org", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((None, b"www.python.org", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", "", b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", None, b"", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", "", b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", None, b"", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", b"", "", b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", b"", None, b""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", b"", b"", ""))
+        with self.assertWarns(DeprecationWarning):
+            urlunsplit((b"http", b"www.python.org", b"", b"", None))
+
+        self.assertWarns(DeprecationWarning, urldefrag, None)
+        self.assertWarns(DeprecationWarning, parse_qsl, None)
+
     def _check_result_type(self, str_type):
         num_args = len(str_type._fields)
         bytes_type = str_type._encoded_counterpart
diff -r fb70ea8b7b2d Lib/urllib/parse.py
--- a/Lib/urllib/parse.py	Tue Apr 26 09:31:11 2016 +0300
+++ b/Lib/urllib/parse.py	Tue Apr 26 14:48:15 2016 +0300
@@ -103,12 +103,26 @@ def _coerce_args(*args):
     # an appropriate result coercion function
     #   - noop for str inputs
     #   - encoding function otherwise
-    str_input = isinstance(args[0], str)
+    arg = args[0]
+    if isinstance(arg, str):
+        str_input = True
+    else:
+        str_input = False
+        if not (arg or hasattr(arg, 'decode')):
+            import warnings
+            warnings.warn('Use of %r is deprecated' % (arg,),
+                          DeprecationWarning, 3)
     for arg in args[1:]:
-        # We special-case the empty string to support the
-        # "scheme=''" default argument to some functions
-        if arg and isinstance(arg, str) != str_input:
+        if isinstance(arg, str) == str_input and (str_input or arg or hasattr(arg, 'decode')):
+            continue
+
+        if arg:
             raise TypeError("Cannot mix str and non-str arguments")
+        else:
+            import warnings
+            warnings.warn('Use of %r is deprecated' % (arg,),
+                          DeprecationWarning, 3)
+
     if str_input:
         return args + (_noop,)
     return _decode_args(args) + (_encode_result,)
@@ -347,12 +361,16 @@ def _fix_result_transcoding():
 _fix_result_transcoding()
 del _fix_result_transcoding
 
-def urlparse(url, scheme='', allow_fragments=True):
+_sentinel = object()
+
+def urlparse(url, scheme=_sentinel, allow_fragments=True):
     """Parse a URL into 6 components:
     <scheme>://<netloc>/<path>;<params>?<query>#<fragment>
     Return a 6-tuple: (scheme, netloc, path, params, query, fragment).
     Note that we don't break the components up in smaller bits
     (e.g. netloc is a single string) and we don't expand % escapes."""
+    if scheme is _sentinel:
+        scheme = url[:0]
     url, scheme, _coerce_result = _coerce_args(url, scheme)
     splitresult = urlsplit(url, scheme, allow_fragments)
     scheme, netloc, url, query, fragment = splitresult
@@ -380,12 +398,14 @@ def _splitnetloc(url, start=0):
             delim = min(delim, wdelim)     # use earliest delim position
     return url[start:delim], url[delim:]   # return (domain, rest)
 
-def urlsplit(url, scheme='', allow_fragments=True):
+def urlsplit(url, scheme=_sentinel, allow_fragments=True):
     """Parse a URL into 5 components:
     <scheme>://<netloc>/<path>?<query>#<fragment>
     Return a 5-tuple: (scheme, netloc, path, query, fragment).
     Note that we don't break the components up in smaller bits
     (e.g. netloc is a single string) and we don't expand % escapes."""
+    if scheme is _sentinel:
+        scheme = url[:0]
     url, scheme, _coerce_result = _coerce_args(url, scheme)
     allow_fragments = bool(allow_fragments)
     key = url, scheme, allow_fragments, type(url), type(scheme)