diff --git a/OpenSSL/SSL.py b/OpenSSL/SSL.py
index c8eec9a..2f36655 100644
--- a/OpenSSL/SSL.py
+++ b/OpenSSL/SSL.py
@@ -449,12 +449,7 @@
         :param filetype: (optional) The encoding of the file, default is PEM
         :return: None
         """
-        if isinstance(keyfile, _text_type):
-            # Perhaps sys.getfilesystemencoding() could be better?
-            keyfile = keyfile.encode("utf-8")
-
-        if not isinstance(keyfile, bytes):
-            raise TypeError("keyfile must be a byte string")
+        keyfile = _path_string(keyfile)
 
         if filetype is _unspecified:
             filetype = FILETYPE_PEM
diff --git a/OpenSSL/test/test_ssl.py b/OpenSSL/test/test_ssl.py
index 0b6a5ff..5942200 100644
--- a/OpenSSL/test/test_ssl.py
+++ b/OpenSSL/test/test_ssl.py
@@ -394,23 +394,52 @@
         self.assertRaises(Error, ctx.use_privatekey_file, self.mktemp())
 
 
+    def _use_privatekey_file_test(self, pemfile, filetype):
+        """
+        Verify that calling ``Context.use_privatekey_file`` with the given
+        arguments does not raise an exception.
+        """
+        key = PKey()
+        key.generate_key(TYPE_RSA, 128)
+
+        with open(pemfile, "wt") as pem:
+            pem.write(
+                dump_privatekey(FILETYPE_PEM, key).decode("ascii")
+            )
+
+        ctx = Context(TLSv1_METHOD)
+        ctx.use_privatekey_file(pemfile, filetype)
+
+
+    def test_use_privatekey_file_bytes(self):
+        """
+        A private key can be specified from a file by passing a ``bytes``
+        instance giving the file name to ``Context.use_privatekey_file``.
+        """
+        self._use_privatekey_file_test(
+            self.mktemp() + NON_ASCII.encode(getfilesystemencoding()),
+            FILETYPE_PEM,
+        )
+
+
+    def test_use_privatekey_file_unicode(self):
+        """
+        A private key can be specified from a file by passing a ``unicode``
+        instance giving the file name to ``Context.use_privatekey_file``.
+        """
+        self._use_privatekey_file_test(
+            self.mktemp().decode(getfilesystemencoding()) + NON_ASCII,
+            FILETYPE_PEM,
+        )
+
+
     if not PY3:
         def test_use_privatekey_file_long(self):
             """
             On Python 2 :py:obj:`Context.use_privatekey_file` accepts a
             filetype of type :py:obj:`long` as well as :py:obj:`int`.
             """
-            pemfile = self.mktemp()
-
-            key = PKey()
-            key.generate_key(TYPE_RSA, 128)
-
-            with open(pemfile, "wt") as pem:
-                pem.write(
-                    dump_privatekey(FILETYPE_PEM, key).decode("ascii"))
-
-            ctx = Context(TLSv1_METHOD)
-            ctx.use_privatekey_file(pemfile, long(FILETYPE_PEM))
+            self._use_privatekey_file_test(self.mktemp(), long(FILETYPE_PEM))
 
 
     def test_use_certificate_wrong_args(self):