diff --git a/requests/utils.py b/requests/utils.py
index 8b2a5f145e..e018e717ef 100644
--- a/requests/utils.py
+++ b/requests/utils.py
@@ -21,6 +21,7 @@
 import zipfile
 from collections import OrderedDict
 from urllib3.util import make_headers
+from urllib3.util import parse_url
 
 from .__version__ import __version__
 from . import certs
@@ -963,15 +964,23 @@ def prepend_scheme_if_needed(url, new_scheme):
 
     :rtype: str
     """
-    scheme, netloc, path, params, query, fragment = urlparse(url, new_scheme)
-
-    # urlparse is a finicky beast, and sometimes decides that there isn't a
-    # netloc present. Assume that it's being over-cautious, and switch netloc
-    # and path if urlparse decided there was no netloc.
+    parsed = parse_url(url)
+    scheme, auth, host, port, path, query, fragment = parsed
+
+    # A defect in urlparse determines that there isn't a netloc present in some
+    # urls. We previously assumed parsing was overly cautious, and swapped the
+    # netloc and path. Due to a lack of tests on the original defect, this is
+    # maintained with parse_url for backwards compatibility.
+    netloc = parsed.netloc
     if not netloc:
         netloc, path = path, netloc
 
-    return urlunparse((scheme, netloc, path, params, query, fragment))
+    if scheme is None:
+        scheme = new_scheme
+    if path is None:
+        path = ''
+
+    return urlunparse((scheme, netloc, path, '', query, fragment))
 
 
 def get_auth_from_url(url):
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 559dee657f..c2186b885f 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -601,6 +601,7 @@ def test_parse_header_links(value, expected):
     'value, expected', (
         ('example.com/path', 'http://example.com/path'),
         ('//example.com/path', 'http://example.com/path'),
+        ('example.com:80', 'http://example.com:80'),
     ))
 def test_prepend_scheme_if_needed(value, expected):
     assert prepend_scheme_if_needed(value, 'http') == expected