diff --git a/src/core/model/ptr.h b/src/core/model/ptr.h
index 3188c1fe9..eee94d40a 100644
--- a/src/core/model/ptr.h
+++ b/src/core/model/ptr.h
@@ -780,6 +780,7 @@ template <typename T>
 T *
 Ptr<T>::operator -> () 
 {
+  NS_ASSERT_MSG (m_ptr, "Attempted to dereference zero pointer");
   return m_ptr;
 }
 
@@ -787,6 +788,7 @@ template <typename T>
 T *
 Ptr<T>::operator -> () const
 {
+  NS_ASSERT_MSG (m_ptr, "Attempted to dereference zero pointer");
   return m_ptr;
 }
 
@@ -794,6 +796,7 @@ template <typename T>
 T &
 Ptr<T>::operator * () const
 {
+  NS_ASSERT_MSG (m_ptr, "Attempted to dereference zero pointer");
   return *m_ptr;
 }
 
@@ -801,6 +804,7 @@ template <typename T>
 T &
 Ptr<T>::operator * ()
 {
+  NS_ASSERT_MSG (m_ptr, "Attempted to dereference zero pointer");
   return *m_ptr;
 }