diff --git a/tests/unit/engine_stubs.cpp b/tests/unit/engine_stubs.cpp
index abe5614a..4fe4ab12 100644
--- a/tests/unit/engine_stubs.cpp
+++ b/tests/unit/engine_stubs.cpp
@@ -68,4 +68,11 @@ layer_handle node_layers::close() {
 
 void node_layers::instance_begin(std::string const &, source_span const &) {}
 
+// basic_node has no key function for the Itanium C++ ABI (tooltip() is declared plain but defined inline), so
+// GCC and Clang emit its vtable wherever scenenode.h is used, here too, and the vtable wants radius_().
+// the same as the game's, in scene/scenenode.cpp
+float basic_node::radius_() {
+	return 0.f;
+}
+
 } // namespace scene