--- a/src/core/model/hash.cc	Tue Nov 13 16:31:48 2012 -0800
+++ b/src/core/model/hash.cc	Tue Nov 13 16:32:31 2012 -0800
@@ -33,11 +33,13 @@
 Hash::Hash ()
 {
   m_impl = Create <HashImplNS::Murmur3> ();
+  NS_ASSERT (m_impl != 0);
 }
 
 Hash::Hash (Ptr<HashImplementation> hp)
   : m_impl(hp)
 {
+  NS_ASSERT (m_impl != 0);
 }