diff --git a/CMakeLists.txt b/CMakeLists.txt
index c2e8b74d..be7c1d7f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,3 +25,5 @@ add_subdirectory(utest)
 # provide find_package() support
 
 xo_export_cmake_config(${PROJECT_NAME} ${PROJECT_VERSION} ${PROJECT_NAME}Targets)
+
+# end CMakeLists.txt
diff --git a/include/xo/reflect/pointer/PointerTdx.hpp b/include/xo/reflect/pointer/PointerTdx.hpp
index 037d3ee4..5e59a9d9 100644
--- a/include/xo/reflect/pointer/PointerTdx.hpp
+++ b/include/xo/reflect/pointer/PointerTdx.hpp
@@ -23,6 +23,12 @@ namespace xo {
 
             virtual Metatype metatype() const override { return Metatype::mt_pointer; }
             virtual uint32_t n_child(void * object) const override = 0;
+
+            /* number of children unknown at compile time.
+             * null-pointer -> 0, non-null pointer -> 1
+             */
+            virtual uint32_t n_child_fixed() const override { return 0; /*unknown*/ }
+
             virtual TaggedPtr child_tp(uint32_t i, void * object) const override = 0;
             /* (forbidden) */
             virtual std::string const & struct_member_name(uint32_t i) const override;