diff --git a/django/core/cache/backends/memcached.py b/django/core/cache/backends/memcached.py
index fa0de8dab9..beb8844ec1 100644
--- a/django/core/cache/backends/memcached.py
+++ b/django/core/cache/backends/memcached.py
@@ -17,7 +17,9 @@ class CacheClass(BaseCache):
         self._cache = memcache.Client(server.split(';'))
 
     def add(self, key, value, timeout=0):
-        return self._cache.add(key.encode('ascii', 'ignore'), value, timeout or self.default_timeout)
+        if isinstance(value, unicode):
+            value = value.encode('utf-8')
+        return self._cache.add(smart_str(key), value, timeout or self.default_timeout)
 
     def get(self, key, default=None):
         val = self._cache.get(smart_str(key))