diff --git a/qutebrowser/config/configtypes.py b/qutebrowser/config/configtypes.py
index bd4ecdf94..19b3854b0 100644
--- a/qutebrowser/config/configtypes.py
+++ b/qutebrowser/config/configtypes.py
@@ -833,10 +833,14 @@ class File(BaseType):
             else:
                 raise configexc.ValidationError(value, "may not be empty!")
         value = os.path.expanduser(value)
-        if not os.path.isfile(value):
-            raise configexc.ValidationError(value, "must be a valid file!")
-        if not os.path.isabs(value):
-            raise configexc.ValidationError(value, "must be an absolute path!")
+        try:
+            if not os.path.isfile(value):
+                raise configexc.ValidationError(value, "must be a valid file!")
+            if not os.path.isabs(value):
+                raise configexc.ValidationError(
+                    value, "must be an absolute path!")
+        except UnicodeEncodeError as e:
+            raise configexc.ValidationError(value, e)
 
     def transform(self, value):
         if not value:
@@ -858,11 +862,15 @@ class Directory(BaseType):
                 raise configexc.ValidationError(value, "may not be empty!")
         value = os.path.expandvars(value)
         value = os.path.expanduser(value)
-        if not os.path.isdir(value):
-            raise configexc.ValidationError(value, "must be a valid "
-                                            "directory!")
-        if not os.path.isabs(value):
-            raise configexc.ValidationError(value, "must be an absolute path!")
+        try:
+            if not os.path.isdir(value):
+                raise configexc.ValidationError(
+                    value, "must be a valid directory!")
+            if not os.path.isabs(value):
+                raise configexc.ValidationError(
+                    value, "must be an absolute path!")
+        except UnicodeEncodeError as e:
+            raise configexc.ValidationError(value, e)
 
     def transform(self, value):
         if not value:
@@ -1179,18 +1187,21 @@ class UserStyleSheet(File):
                 raise configexc.ValidationError(value, "may not be empty!")
         value = os.path.expandvars(value)
         value = os.path.expanduser(value)
-        if not os.path.isabs(value):
-            # probably a CSS, so we don't handle it as filename.
-            # FIXME We just try if it is encodable, maybe we should validate
-            # CSS?
-            # https://github.com/The-Compiler/qutebrowser/issues/115
-            try:
-                value.encode('utf-8')
-            except UnicodeEncodeError as e:
-                raise configexc.ValidationError(value, str(e))
-            return
-        elif not os.path.isfile(value):
-            raise configexc.ValidationError(value, "must be a valid file!")
+        try:
+            if not os.path.isabs(value):
+                # probably a CSS, so we don't handle it as filename.
+                # FIXME We just try if it is encodable, maybe we should
+                # validate CSS?
+                # https://github.com/The-Compiler/qutebrowser/issues/115
+                try:
+                    value.encode('utf-8')
+                except UnicodeEncodeError as e:
+                    raise configexc.ValidationError(value, str(e))
+                return
+            elif not os.path.isfile(value):
+                raise configexc.ValidationError(value, "must be a valid file!")
+        except UnicodeEncodeError as e:
+            raise configexc.ValidationError(value, e)
 
     def transform(self, value):
         path = os.path.expandvars(value)
diff --git a/qutebrowser/test/config/test_configtypes.py b/qutebrowser/test/config/test_configtypes.py
index 633dc0e32..a922e6fde 100644
--- a/qutebrowser/test/config/test_configtypes.py
+++ b/qutebrowser/test/config/test_configtypes.py
@@ -1374,6 +1374,13 @@ class FileTests(unittest.TestCase):
         self.t.validate('~/foobar')
         os_path.expanduser.assert_called_once_with('~/foobar')
 
+    def test_validate_invalid_encoding(self, os_path):
+        """Test validate with an invalid encoding, e.g. LC_ALL=C."""
+        os_path.isfile.side_effect = helpers.unicode_encode_err
+        os_path.isabs.side_effect = helpers.unicode_encode_err
+        with self.assertRaises(configexc.ValidationError):
+            self.t.validate('foobar')
+
     def test_transform(self, os_path):
         """Test transform."""
         os_path.expanduser.side_effect = lambda x: x.replace('~', '/home/foo')
@@ -1445,6 +1452,13 @@ class DirectoryTests(unittest.TestCase):
             self.t.validate('$BAR/foobar')
             os_path.expandvars.assert_called_once_with('$BAR/foobar')
 
+    def test_validate_invalid_encoding(self, os_path):
+        """Test validate with an invalid encoding, e.g. LC_ALL=C."""
+        os_path.isdir.side_effect = helpers.unicode_encode_err
+        os_path.isabs.side_effect = helpers.unicode_encode_err
+        with self.assertRaises(configexc.ValidationError):
+            self.t.validate('foobar')
+
     def test_transform(self, os_path):
         """Test transform."""
         os_path.expandvars.side_effect = lambda x: x
@@ -1879,6 +1893,14 @@ class UserStyleSheetTests(unittest.TestCase):
     def setUp(self):
         self.t = configtypes.UserStyleSheet()
 
+    @mock.patch('qutebrowser.config.configtypes.os.path', autospec=True)
+    def test_validate_invalid_encoding(self, os_path):
+        """Test validate with an invalid encoding, e.g. LC_ALL=C."""
+        os_path.isfile.side_effect = helpers.unicode_encode_err
+        os_path.isabs.side_effect = helpers.unicode_encode_err
+        with self.assertRaises(configexc.ValidationError):
+            self.t.validate('foobar')
+
     def test_transform_empty(self):
         """Test transform with an empty value."""
         self.assertIsNone(self.t.transform(''))
diff --git a/qutebrowser/test/helpers.py b/qutebrowser/test/helpers.py
index 873312ab0..23ef2b25e 100644
--- a/qutebrowser/test/helpers.py
+++ b/qutebrowser/test/helpers.py
@@ -29,6 +29,13 @@ from PyQt5.QtWebKitWidgets import QWebPage
 from PyQt5.QtNetwork import QNetworkAccessManager
 
 
+unicode_encode_err = UnicodeEncodeError('ascii',           # codec
+                                        '',                # object
+                                        0,                 # start
+                                        2,                 # end
+                                        'fake exception')  # reason
+
+
 @contextlib.contextmanager
 def environ_set_temp(env):
     """Set temporary environment variables.