diff --git a/scene/main/scene_tree.cpp b/scene/main/scene_tree.cpp
index 9aaddfd373..66f3a2ebde 100644
--- a/scene/main/scene_tree.cpp
+++ b/scene/main/scene_tree.cpp
@@ -389,6 +389,7 @@ void SceneTree::set_group(const StringName &p_group, const String &p_name, const
 }
 
 void SceneTree::initialize() {
+	ERR_FAIL_COND(!root);
 	initialized = true;
 	root->_set_tree(this);
 	MainLoop::initialize();