diff --git a/src/wren/vm.hpp b/src/wren/vm.hpp
index 4394175..d46c59e 100644
--- a/src/wren/vm.hpp
+++ b/src/wren/vm.hpp
@@ -14,14 +14,14 @@ namespace wren {
 
 	namespace detail {
 		struct Callbacks {
-			void (*write_fn)(Configuration&, VM*, const char*);
-			void (*error_fn)(Configuration&, VM*, ErrorType, const char*, int, const char*);
-			void* (*reallocate_fn)(void*, std::size_t);
-			const char* (*resolve_module_fn)(Configuration&, VM*, const char*, const char*);
-			char* (*load_module_fn)(Configuration&, VM*, const char*);
+			void (*write_fn)(Configuration&, VM*, const char*) {nullptr};
+			void (*error_fn)(Configuration&, VM*, ErrorType, const char*, int, const char*) {nullptr};
+			void* (*reallocate_fn)(void*, std::size_t) {nullptr};
+			const char* (*resolve_module_fn)(Configuration&, VM*, const char*, const char*) {nullptr};
+			char* (*load_module_fn)(Configuration&, VM*, const char*) {nullptr};
 
-			Configuration* config_obj;
-			VM* vm;
+			Configuration* config_obj {nullptr};
+			VM* vm {nullptr};
 		};
 	} //namespace detail
 
@@ -72,41 +72,27 @@ namespace wren {
 
 	template <typename T>
 	inline detail::Callbacks VM::to_callbacks (T& conf) {
-		using detail::method_write;
-		using detail::method_error;
 		using detail::method_reallocate;
-		using detail::method_resolve_module;
-		using detail::method_load_module;
 
 		detail::Callbacks ret;
 		ret.config_obj = &conf;
 		ret.vm = this;
 
-		if constexpr (method_write::exists<T>::value)
+		if constexpr (detail::method_write::exists<T>::value)
 			ret.write_fn = &detail::AnyFunctionWrap<T, decltype(&T::write_fn)>::template call<&T::write_fn>;
-		else
-			ret.write_fn = nullptr;
 
-		if constexpr (method_error::exists<T>::value)
+		if constexpr (detail::method_error::exists<T>::value)
 			ret.error_fn = &detail::AnyFunctionWrap<T, decltype(&T::error_fn)>::template call<&T::error_fn>;
-		else
-			ret.error_fn = nullptr;
 
 		if constexpr (method_reallocate::exists<T>::value and method_reallocate::is_static<T>::value)
 			ret.reallocate_fn = &T::reallocate_fn;
-		else
-			ret.reallocate_fn = nullptr;
 		static_assert(not method_reallocate::exists<T>::value or method_reallocate::is_static<T>::value, "Realloc function must be a static function");
 
-		if constexpr (method_resolve_module::exists<T>::value)
+		if constexpr (detail::method_resolve_module::exists<T>::value)
 			ret.resolve_module_fn = &detail::AnyFunctionWrap<T, decltype(&T::resolve_module_fn)>::template call<&T::resolve_module_fn>;
-		else
-			ret.resolve_module_fn = nullptr;
 
-		if constexpr (method_load_module::exists<T>::value)
+		if constexpr (detail::method_load_module::exists<T>::value)
 			ret.load_module_fn = &detail::AnyFunctionWrap<T, decltype(&T::load_module_fn)>::template call<&T::load_module_fn>;
-		else
-			ret.load_module_fn = nullptr;
 
 		return ret;
 	}