diff --git a/letsencrypt/le_util.py b/letsencrypt/le_util.py
index c8a9d24c2..cb1c61074 100644
--- a/letsencrypt/le_util.py
+++ b/letsencrypt/le_util.py
@@ -6,6 +6,7 @@ import logging
 import os
 import platform
 import re
+import six
 import socket
 import stat
 import subprocess
@@ -310,10 +311,13 @@ def enforce_domain_sanity(domain):
     # Unicode
     try:
         domain = domain.encode('ascii').lower()
-    except UnicodeDecodeError:
-        raise errors.ConfigurationError(
-            "Internationalized domain names are not presently supported: {0}"
-            .format(domain))
+    except UnicodeError:
+        error_fmt = (u"Internationalized domain names "
+                      "are not presently supported: {0}")
+        if isinstance(domain, six.text_type):
+            raise errors.ConfigurationError(error_fmt.format(domain))
+        else:
+            raise errors.ConfigurationError(str(error_fmt).format(domain))
 
     # Remove trailing dot
     domain = domain[:-1] if domain.endswith('.') else domain
diff --git a/letsencrypt/tests/le_util_test.py b/letsencrypt/tests/le_util_test.py
index 191b70801..0f9464c6f 100644
--- a/letsencrypt/tests/le_util_test.py
+++ b/letsencrypt/tests/le_util_test.py
@@ -323,5 +323,21 @@ class AddDeprecatedArgumentTest(unittest.TestCase):
         self.assertTrue("--old-option" not in stdout.getvalue())
 
 
+class EnforceDomainSanityTest(unittest.TestCase):
+    """Test enforce_domain_sanity."""
+
+    def _call(self, domain):
+        from letsencrypt.le_util import enforce_domain_sanity
+        return enforce_domain_sanity(domain)
+
+    def test_nonascii_str(self):
+        self.assertRaises(errors.ConfigurationError, self._call,
+                          u"eichh\u00f6rnchen.example.com".encode("utf-8"))
+
+    def test_nonascii_unicode(self):
+        self.assertRaises(errors.ConfigurationError, self._call,
+                          u"eichh\u00f6rnchen.example.com")
+
+
 if __name__ == "__main__":
     unittest.main()  # pragma: no cover