diff --git a/src/internet/model/ipv4-interface.cc b/src/internet/model/ipv4-interface.cc
index 8abb4607b..392a48854 100644
--- a/src/internet/model/ipv4-interface.cc
+++ b/src/internet/model/ipv4-interface.cc
@@ -328,7 +328,10 @@ Ipv4Interface::GetAddress (uint32_t index) const
           ++tmp;
         }
     }
-  NS_ASSERT (false);  // Assert if not found
+  else
+    {
+      NS_FATAL_ERROR ("index " << index << " out of bounds");  
+    }
   Ipv4InterfaceAddress addr;
   return (addr);  // quiet compiler
 }
@@ -339,7 +342,7 @@ Ipv4Interface::RemoveAddress (uint32_t index)
   NS_LOG_FUNCTION (this << index);
   if (index >= m_ifaddrs.size ())
     {
-      NS_ASSERT_MSG (false, "Bug in Ipv4Interface::RemoveAddress");
+      NS_FATAL_ERROR ("Bug in Ipv4Interface::RemoveAddress");
     }
   Ipv4InterfaceAddressListI i = m_ifaddrs.begin ();
   uint32_t tmp = 0;
@@ -354,7 +357,7 @@ Ipv4Interface::RemoveAddress (uint32_t index)
       ++tmp;
       ++i;
     }
-  NS_ASSERT_MSG (false, "Address " << index << " not found");
+  NS_FATAL_ERROR ("Address " << index << " not found");
   Ipv4InterfaceAddress addr;
   return (addr);  // quiet compiler
 }
diff --git a/src/internet/model/ipv6-interface.cc b/src/internet/model/ipv6-interface.cc
index ef730b002..b6e4b5a31 100644
--- a/src/internet/model/ipv6-interface.cc
+++ b/src/internet/model/ipv6-interface.cc
@@ -114,7 +114,7 @@ void Ipv6Interface::DoSetup ()
         }
       else
         {
-          NS_ASSERT_MSG (false, "IPv6 autoconf for this kind of address not implemented.");
+          NS_FATAL_ERROR ("IPv6 autoconf for this kind of address not implemented.");
         }
     }
   else
@@ -299,8 +299,10 @@ Ipv6InterfaceAddress Ipv6Interface::GetAddress (uint32_t index) const
           i++;
         }
     }
-
-  NS_ASSERT_MSG (false, "Address " << index << " not found");
+  else
+    {
+      NS_FATAL_ERROR ("index " << index << " out of bounds");
+    }
   Ipv6InterfaceAddress addr;
   return addr;  /* quiet compiler */
 }
@@ -318,7 +320,7 @@ Ipv6InterfaceAddress Ipv6Interface::RemoveAddress (uint32_t index)
 
   if (m_addresses.size () < index)
     {
-      NS_ASSERT_MSG (false, "Try to remove index that don't exist in Ipv6Interface::RemoveAddress");
+      NS_FATAL_ERROR ("Removing index that does not exist in Ipv6Interface::RemoveAddress");
     }
 
   for (Ipv6InterfaceAddressListI it = m_addresses.begin (); it != m_addresses.end (); ++it)
@@ -332,8 +334,7 @@ Ipv6InterfaceAddress Ipv6Interface::RemoveAddress (uint32_t index)
 
       i++;
     }
-
-  NS_ASSERT_MSG (false, "Address " << index << " not found");
+  NS_FATAL_ERROR ("Address " << index << " not found");
   Ipv6InterfaceAddress addr;
   return addr;  /* quiet compiler */
 }