diff --git a/Kernel/Types/generic_tree.hpp b/Kernel/Types/generic_tree.hpp
index 147fb748e..61e76555f 100644
--- a/Kernel/Types/generic_tree.hpp
+++ b/Kernel/Types/generic_tree.hpp
@@ -13,6 +13,7 @@
 #define GENERIC_TREE_H
 
 #include "blackbox.hpp"
+#include "tree.hpp"
 
 class generic_rep : public tree_rep {
 public:
diff --git a/tests/Kernel/Types/generic_tree_test.cpp b/tests/Kernel/Types/generic_tree_test.cpp
new file mode 100644
index 000000000..705e8acac
--- /dev/null
+++ b/tests/Kernel/Types/generic_tree_test.cpp
@@ -0,0 +1,11 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+
+#include "doctest/doctest.h"
+#include "generic_tree.hpp"
+#include "tree.hpp"
+
+TEST_CASE ("test as") {
+  CHECK_EQ (as<double, int> (1), 1.0);
+  CHECK_EQ (as<int, double> (1.0), 1);
+  CHECK_EQ (as<int, double> (1.5), 1);
+}