diff --git a/requests/utils.py b/requests/utils.py
index fd186b88..6892713a 100644
--- a/requests/utils.py
+++ b/requests/utils.py
@@ -706,6 +706,10 @@ def should_bypass_proxies(url, no_proxy):
         no_proxy = get_proxy('no_proxy')
     parsed = urlparse(url)
 
+    if parsed.hostname is None:
+        # URLs don't always have hostnames, e.g. file:/// urls.
+        return True
+
     if no_proxy:
         # We need to check whether we match here. We need to see if we match
         # the end of the hostname, both with and without the port.
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 70ffa5fb..f34c630f 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -622,6 +622,7 @@ def test_urldefragauth(url, expected):
             ('http://172.16.1.12/', False),
             ('http://172.16.1.12:5000/', False),
             ('http://google.com:5000/v1.0/', False),
+            ('file:///some/path/on/disk', True),
     ))
 def test_should_bypass_proxies(url, expected, monkeypatch):
     """Tests for function should_bypass_proxies to check if proxy