diff --git a/nova/process.py b/nova/process.py
index d3558ed2..8ecef158 100644
--- a/nova/process.py
+++ b/nova/process.py
@@ -205,13 +205,12 @@ class ProcessPool(object):
         self._pool.release()
         return rv
 
-class SharedPool(ProcessPool):
-    _instance = None
-    def __new__(cls, *args, **kwargs):
-        if not cls._instance:
-            cls._instance = super(SharedPool, cls).__new__(
-                    cls, *args, **kwargs)
-        return cls._instance
+_instance = None
+def SharedPool():
+    global _instance
+    if _instance is None:
+       _instance = ProcessPool()
+    return _instance
 
 def simple_execute(cmd, **kwargs):
     return SharedPool().simple_execute(cmd, **kwargs)
diff --git a/nova/tests/process_unittest.py b/nova/tests/process_unittest.py
index 1c15b69a..c96bb591 100644
--- a/nova/tests/process_unittest.py
+++ b/nova/tests/process_unittest.py
@@ -120,3 +120,10 @@ class ProcessTestCase(test.TrialTestCase):
         pool2 = process.SharedPool()
         self.assert_(id(pool1) == id(pool2))
 
+    def test_shared_pool_works_as_singleton(self):
+        d1 = process.simple_execute('sleep 1')
+        d2 = process.simple_execute('sleep 0.005')
+        # lp609749: would have failed with
+        # exceptions.AssertionError: Someone released me too many times:
+        # too many tokens!
+        return d1