diff --git a/src/core/model/type-id.cc b/src/core/model/type-id.cc
index 9038077b7..d865cca44 100644
--- a/src/core/model/type-id.cc
+++ b/src/core/model/type-id.cc
@@ -215,6 +215,7 @@ IidManager::AllocateUid (std::string name)
   information.hash = hash;
   information.parent = 0;
   information.groupName = "";
+  information.size = (std::size_t)(-1);
   information.hasConstructor = false;
   information.mustHideFromDocumentation = false;
   m_information.push_back (information);
diff --git a/src/core/model/type-id.h b/src/core/model/type-id.h
index eb1da98c9..d48699290 100644
--- a/src/core/model/type-id.h
+++ b/src/core/model/type-id.h
@@ -252,6 +252,9 @@ public:
    * \code
    *   SetSize (sizeof (<typename>));
    * \endcode
+   * This is done automatically by NS_LOG_ENSURE_REGISTERED()
+   * A ridiculously large reported size is a symptom that the
+   * type hasn't been registered.
    *
    * \param size The size of the object, in bytes.
    * \returns this TypeId instance.