diff --git a/klein/resource.py b/klein/resource.py
index 4e0fae90f..151ee90b1 100644
--- a/klein/resource.py
+++ b/klein/resource.py
@@ -8,7 +8,17 @@
 
 from klein.interfaces import IKleinRequest
 
-__all__ = ["KleinResource"]
+__all__ = ["KleinResource", "ensure_utf8_bytes"]
+
+
+def ensure_utf8_bytes(v):
+    """
+    Coerces a value which is either a C{unicode} or C{str} to a C{str}.
+    If ``v`` is a C{unicode} object it is encoded as utf-8.
+    """
+    if isinstance(v, unicode):
+        v = v.encode("utf-8")
+    return v
 
 
 class KleinResource(Resource):
@@ -63,9 +73,9 @@ def render(self, request):
             resp = he.get_response({})
 
             for header, value in resp.headers:
-                request.setHeader(header, value)
+                request.setHeader(ensure_utf8_bytes(header), ensure_utf8_bytes(value))
 
-            return he.get_body({})
+            return ensure_utf8_bytes(he.get_body({}))
 
         # Try pretty hard to fix up prepath and postpath.
         segment_count = self._app.endpoints[endpoint].segment_count
diff --git a/klein/test_resource.py b/klein/test_resource.py
index 049f0114d..d8a17bb47 100644
--- a/klein/test_resource.py
+++ b/klein/test_resource.py
@@ -5,7 +5,7 @@
 from twisted.trial import unittest
 
 from klein import Klein
-from klein.resource import KleinResource
+from klein.resource import KleinResource, ensure_utf8_bytes
 from klein.interfaces import IKleinRequest
 
 from twisted.internet.defer import succeed, Deferred
@@ -653,3 +653,8 @@ def _cb(result):
         d.addCallback(_cb)
         return d
 
+
+    def test_ensure_utf8_bytes(self):
+        self.assertEqual(ensure_utf8_bytes(u"abc"), "abc")
+        self.assertEqual(ensure_utf8_bytes(u"\u2202"), "\xe2\x88\x82")
+        self.assertEqual(ensure_utf8_bytes("\xe2\x88\x82"), "\xe2\x88\x82")