diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py
index 69d65c1..e559142 100644
--- a/Lib/test/test_urlparse.py
+++ b/Lib/test/test_urlparse.py
@@ -461,6 +461,27 @@
         self.assertEqual(urllib.parse.urlparse("http://example.com?blahblah=/foo"),
                          ('http', 'example.com', '', '', 'blahblah=/foo', ''))
 
+    def test_withoutscheme(self):
+        # Test urlparse without scheme
+        # Issue 754016: urlparse goes wrong with IP:port without scheme
+        # RFC 1808 specifies that netloc should start with //, urlparse expects
+        # the same, otherwise it classifies the portion of url as path.
+        self.assertEqual(urllib.parse.urlparse("path"),
+                ('','','path','','',''))
+        self.assertEqual(urllib.parse.urlparse("//www.python.org:80"),
+                ('','www.python.org:80','','','',''))
+        self.assertEqual(urllib.parse.urlparse("http://www.python.org:80"),
+                ('http','www.python.org:80','','','',''))
+
+    def test_portseparator(self):
+        # Issue 754016 makes changes for port separator ':' from scheme separator
+        self.assertEqual(urllib.parse.urlparse("path:80"),
+                ('','','path:80','','',''))
+        self.assertEqual(urllib.parse.urlparse("http:"),('http','','','','',''))
+        self.assertEqual(urllib.parse.urlparse("https:"),('https','','','','',''))
+        self.assertEqual(urllib.parse.urlparse("http://www.python.org:80"),
+                ('http','www.python.org:80','','','',''))
+
     def test_usingsys(self):
         # Issue 3314: sys module is used in the error
         self.assertRaises(TypeError, urllib.parse.urlencode, "foo")
diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
index 133b9d9..00f0e5b 100644
--- a/Lib/urllib/parse.py
+++ b/Lib/urllib/parse.py
@@ -192,11 +192,12 @@
             v = SplitResult(scheme, netloc, url, query, fragment)
             _parse_cache[key] = v
             return v
-        for c in url[:i]:
-            if c not in scheme_chars:
-                break
-        else:
-            scheme, url = url[:i].lower(), url[i+1:]
+        if url.endswith(':') or not url[i+1].isdigit():
+            for c in url[:i]:
+                if c not in scheme_chars:
+                    break
+            else:
+                scheme, url = url[:i].lower(), url[i+1:]
     if url[:2] == '//':
         netloc, url = _splitnetloc(url, 2)
         if (('[' in netloc and ']' not in netloc) or