diff --git a/sphinx/search.py b/sphinx/search.py
index 729b63b2a..6d5a0614d 100644
--- a/sphinx/search.py
+++ b/sphinx/search.py
@@ -58,10 +58,13 @@ class _JavaScriptIndex(object):
         return jsdump.loads(data)
 
     def dump(self, data, f):
-        f.write(self.dumps(data))
+        f.write(self.dumps(data).encode('utf-8'))
 
     def load(self, f):
-        return self.loads(f.read())
+        data = f.read()
+        if isinstance(data, unicode):
+            return self.loads(data)
+        return self.loads(data.decode('utf-8'))
 
 
 js_index = _JavaScriptIndex()