diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4b03772..83dea4a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,7 +27,7 @@ macro(compile_options target_name)
     sanitizers(${target_name})
 endmacro()
 
-project(blt-gp VERSION 0.5.15)
+project(blt-gp VERSION 0.5.16)
 
 include(CTest)
 
diff --git a/lib/blt b/lib/blt
index 2bac310..fb09242 160000
--- a/lib/blt
+++ b/lib/blt
@@ -1 +1 @@
-Subproject commit 2bac310e55df06a3e378c932afa2a4c2bc2123e7
+Subproject commit fb092422a82e503d314fc5c99eacb306c29386e8
diff --git a/src/program.cpp b/src/program.cpp
index 48b6db1..95ca853 100644
--- a/src/program.cpp
+++ b/src/program.cpp
@@ -17,6 +17,7 @@
  */
 #include <blt/gp/program.h>
 #include <iostream>
+#include <blt/std/variant.h>
 
 #ifndef BLT_ASSERT_RET
 #define BLT_ASSERT_RET(expr) if (!(expr)) { return false; }
diff --git a/tests/serialization_test.cpp b/tests/serialization_test.cpp
index 09fa1cd..8d9ca95 100644
--- a/tests/serialization_test.cpp
+++ b/tests/serialization_test.cpp
@@ -26,59 +26,48 @@
 #include <fstream>
 #include <blt/fs/stream_wrappers.h>
 
-
-struct no_default
+struct default_type
 {
-    no_default() = delete;
-
-    no_default(int)
+    std::string to_string() // NOLINT
     {
+        return "Unimplemented";
     }
 };
 
-struct not_copyable
+struct type1 : default_type
 {
-    not_copyable() = default;
-    not_copyable(const not_copyable&) = delete;
+    std::string to_string() // NOLINT
+    {
+        return "type1";
+    }
 };
 
-struct copyable
+struct type2 : default_type
 {
-    copyable() = default;
-    copyable(const copyable&) = default;
+    std::string to_string() // NOLINT
+    {
+        return "type2";
+    }
 };
 
-struct copyable_nothrow
+struct type3 : default_type
 {
-    copyable_nothrow() = default;
-    copyable_nothrow(const copyable_nothrow&) noexcept = default;
+    std::string to_string() // NOLINT
+    {
+        return "type3";
+    }
 };
 
-struct not_movable
+void test()
 {
-    not_movable() = default;
-    not_movable(not_movable&&) = delete;
-};
+    blt::variant_t<type1, type2, type3> some_type1{type1{}};
+    blt::variant_t<type1, type2, type3> some_type2{type2{}};
+    blt::variant_t<type1, type2, type3> some_type3{type3{}};
 
-struct movable
-{
-    movable() = default;
-    movable(movable&&) = delete;
-};
-
-struct movable_nothrow
-{
-    movable_nothrow() = default;
-    movable_nothrow(movable_nothrow&&) noexcept = delete;
-};
-
-blt::variant_t<no_default> no_default_variant;
-blt::variant_t<not_copyable> not_copyable_variant;
-blt::variant_t<copyable> copyable_variant;
-blt::variant_t<copyable_nothrow> copyable_nothrow_variant;
-blt::variant_t<not_movable> not_movable_variant;
-blt::variant_t<movable> movable_variant;
-blt::variant_t<movable_nothrow> movable_nothrow_variant;
+    BLT_TRACE("TYPE1: {}", some_type1.call_member(&default_type::to_string));
+    BLT_TRACE("TYPE2: {}", some_type2.call_member(&default_type::to_string));
+    BLT_TRACE("TYPE3: {}", some_type3.call_member(&default_type::to_string));
+}
 
 using namespace blt::gp;
 
@@ -144,6 +133,8 @@ bool fitness_function(const tree_t& current_tree, fitness_t& fitness, size_t)
 
 int main()
 {
+    test();
+    return 0;
     operator_builder<context> builder{};
     const auto& operators = builder.build(addf, subf, mulf, pro_divf, op_sinf, op_cosf, op_expf, op_logf, litf, op_xf);
     regression.get_program().set_operations(operators);