--- a/genshi/core.py
+++ b/genshi/core.py
@@ -22,6 +22,11 @@
 
 class StreamEventKind(str):
     """A kind of event on an XML stream."""
+    __slots__ = []
+    _instances = {}
+
+    def __new__(cls, val):
+        return cls._instances.setdefault(val, str.__new__(cls, val))
 
 
 class Stream(object):
@@ -503,6 +508,15 @@
             return uri
         return object.__new__(cls, uri)
 
+    def __getnewargs__(self):
+        return (self.uri,)
+
+    def __getstate__(self):
+        return self.uri
+
+    def __setstate__(self, uri):
+        self.uri = uri
+
     def __init__(self, uri):
         self.uri = unicode(uri)
 
@@ -572,3 +586,6 @@
             self = unicode.__new__(cls, qname)
             self.namespace, self.localname = None, unicode(qname)
         return self
+
+    def __getnewargs__(self):
+        return (self.lstrip('{'),)