diff --git a/mitmproxy/proxy/protocol/tls.py b/mitmproxy/proxy/protocol/tls.py
index 940ab9ea8..7b6b506cd 100644
--- a/mitmproxy/proxy/protocol/tls.py
+++ b/mitmproxy/proxy/protocol/tls.py
@@ -7,7 +7,7 @@ import netlib.exceptions
 from mitmproxy import exceptions
 from mitmproxy.contrib.tls import _constructs
 from mitmproxy.proxy.protocol import base
-from netlib import utils
+from netlib import check
 
 
 # taken from https://testssl.sh/openssl-rfc.mappping.html
@@ -265,7 +265,7 @@ class TlsClientHello:
                 extension.type == 0x00 and
                 len(extension.server_names) == 1 and
                 extension.server_names[0].type == 0 and
-                utils.is_valid_host(extension.server_names[0].name)
+                check.is_valid_host(extension.server_names[0].name)
             )
             if is_valid_sni_extension:
                 return extension.server_names[0].name.decode("idna")
diff --git a/netlib/utils.py b/netlib/check.py
similarity index 100%
rename from netlib/utils.py
rename to netlib/check.py
diff --git a/netlib/http/http1/read.py b/netlib/http/http1/read.py
index 4c00a96ab..89b73c5ad 100644
--- a/netlib/http/http1/read.py
+++ b/netlib/http/http1/read.py
@@ -6,7 +6,7 @@ from netlib.http import request
 from netlib.http import response
 from netlib.http import headers
 from netlib.http import url
-from netlib import utils
+from netlib import check
 from netlib import exceptions
 
 
@@ -274,7 +274,7 @@ def _parse_authority_form(hostport):
     try:
         host, port = hostport.split(b":")
         port = int(port)
-        if not utils.is_valid_host(host) or not utils.is_valid_port(port):
+        if not check.is_valid_host(host) or not check.is_valid_port(port):
             raise ValueError()
     except ValueError:
         raise exceptions.HttpSyntaxException("Invalid host specification: {}".format(hostport))
diff --git a/netlib/http/url.py b/netlib/http/url.py
index 67e22efa5..3ca581202 100644
--- a/netlib/http/url.py
+++ b/netlib/http/url.py
@@ -2,7 +2,7 @@ import urllib
 from typing import Sequence
 from typing import Tuple
 
-from netlib import utils
+from netlib import check
 
 
 # PY2 workaround
@@ -62,9 +62,9 @@ def parse(url):
     if not full_path.startswith(b"/"):
         full_path = b"/" + full_path
 
-    if not utils.is_valid_host(host):
+    if not check.is_valid_host(host):
         raise ValueError("Invalid Host")
-    if not utils.is_valid_port(port):
+    if not check.is_valid_port(port):
         raise ValueError("Invalid Port")
 
     return parsed.scheme, host, port, full_path
diff --git a/netlib/socks.py b/netlib/socks.py
index 30fe1c9d9..377308a81 100644
--- a/netlib/socks.py
+++ b/netlib/socks.py
@@ -2,7 +2,8 @@ import struct
 import array
 import ipaddress
 
-from netlib import tcp, utils
+from netlib import tcp
+from netlib import check
 from mitmproxy.types import bidi
 
 
@@ -204,7 +205,7 @@ class Message:
         elif atyp == ATYP.DOMAINNAME:
             length, = struct.unpack("!B", f.safe_read(1))
             host = f.safe_read(length)
-            if not utils.is_valid_host(host):
+            if not check.is_valid_host(host):
                 raise SocksError(REP.GENERAL_SOCKS_SERVER_FAILURE, "Invalid hostname: %s" % host)
             host = host.decode("idna")
             use_ipv6 = False
diff --git a/test/mitmproxy/test_flow.py b/test/mitmproxy/test_flow.py
index 9ebcca344..9b7e73950 100644
--- a/test/mitmproxy/test_flow.py
+++ b/test/mitmproxy/test_flow.py
@@ -1,7 +1,7 @@
 import mock
 import io
 
-import netlib.utils
+import netlib.tutils
 from netlib.http import Headers
 import mitmproxy.io
 from mitmproxy import flowfilter, options
diff --git a/test/mitmproxy/tutils.py b/test/mitmproxy/tutils.py
index 71dd20a46..aa70c0e8e 100644
--- a/test/mitmproxy/tutils.py
+++ b/test/mitmproxy/tutils.py
@@ -9,7 +9,6 @@ from unittest.case import SkipTest
 
 import io
 
-import netlib.utils
 import netlib.tutils
 from mitmproxy import controller
 from mitmproxy import connections
diff --git a/test/netlib/test_check.py b/test/netlib/test_check.py
new file mode 100644
index 000000000..6a1388f4d
--- /dev/null
+++ b/test/netlib/test_check.py
@@ -0,0 +1,10 @@
+# coding=utf-8
+
+from netlib import check
+
+
+def test_is_valid_host():
+    assert not check.is_valid_host(b"")
+    assert check.is_valid_host(b"one.two")
+    assert not check.is_valid_host(b"one" * 255)
+    assert check.is_valid_host(b"one.two.")
diff --git a/test/netlib/test_utils.py b/test/netlib/test_utils.py
deleted file mode 100644
index db33fa31e..000000000
--- a/test/netlib/test_utils.py
+++ /dev/null
@@ -1,10 +0,0 @@
-# coding=utf-8
-
-from netlib import utils
-
-
-def test_is_valid_host():
-    assert not utils.is_valid_host(b"")
-    assert utils.is_valid_host(b"one.two")
-    assert not utils.is_valid_host(b"one" * 255)
-    assert utils.is_valid_host(b"one.two.")