diff --git a/lib/pddlparse/include/pddlparse/detail/ASTCopy.h b/lib/pddlparse/include/pddlparse/detail/ASTCopy.h
index 2079a80..2b19b34 100644
--- a/lib/pddlparse/include/pddlparse/detail/ASTCopy.h
+++ b/lib/pddlparse/include/pddlparse/detail/ASTCopy.h
@@ -128,16 +128,6 @@ At<Argument> deepCopy(At<Argument> &other)
 	return At<Argument>(other.timePoint, std::move(argument));
 }
 
-////////////////////////////////////////////////////////////////////////////////////////////////////
-/*
-template<class Argument>
-Either<Argument> deepCopy(Either<Argument> &other)
-{
-	auto argument{deepCopy(other.argument)};
-
-	return Not<Argument>(std::move(argument));
-}*/
-
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 template<class Argument>
@@ -152,20 +142,9 @@ Not<Argument> deepCopy(Not<Argument> &other)
 // Variants
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-struct DeepCopyVisitor
-{
-	template<class Argument>
-	Argument visit(Argument &other)
-	{
-		return deepCopy(other);
-	}
-};
-
-////////////////////////////////////////////////////////////////////////////////////////////////////
-
 ast::Type deepCopy(ast::Type &other)
 {
-	return other.match([](auto &x){deepCopy(x); return std::make_unique<ast::PrimitiveType>(nullptr);});
+	return other.match([](auto &x) -> ast::Type {return deepCopy(x);});
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/lib/pddlparse/src/pddlparse/detail/parsing/Type.cpp b/lib/pddlparse/src/pddlparse/detail/parsing/Type.cpp
index 803f8b3..5b74b3d 100644
--- a/lib/pddlparse/src/pddlparse/detail/parsing/Type.cpp
+++ b/lib/pddlparse/src/pddlparse/detail/parsing/Type.cpp
@@ -23,9 +23,8 @@ ast::Type parseType(Context &context, ast::Domain &domain)
 
 	if (tokenizer.testAndReturn<char>('('))
 	{
-		// TODO: put into Type parsing unit
 		// TODO: refactor
-		auto p =
+		auto parsePrimitiveTypeWrapper =
 			[](auto &context, auto &astContext, auto &) -> std::experimental::optional<ast::PrimitiveTypePointer>
 			{
 				return parsePrimitiveType(context, *astContext.domain);
@@ -35,7 +34,7 @@ ast::Type parseType(Context &context, ast::Domain &domain)
 		ASTContext astContext(domain);
 		VariableStack variableStack;
 
-		auto eitherType = parseEither<ast::PrimitiveTypePointer>(context, astContext, variableStack, p);
+		auto eitherType = parseEither<ast::PrimitiveTypePointer>(context, astContext, variableStack, parsePrimitiveTypeWrapper);
 
 		if (!eitherType)
 			throw ParserException(tokenizer.location(), "expected primitive type or “either” expression");
diff --git a/lib/pddlparse/src/pddlparse/detail/parsing/VariableDeclaration.cpp b/lib/pddlparse/src/pddlparse/detail/parsing/VariableDeclaration.cpp
index fdd3735..dfa25c1 100644
--- a/lib/pddlparse/src/pddlparse/detail/parsing/VariableDeclaration.cpp
+++ b/lib/pddlparse/src/pddlparse/detail/parsing/VariableDeclaration.cpp
@@ -49,13 +49,12 @@ ast::VariableDeclarations parseVariableDeclarations(Context &context, ast::Domai
 			continue;
 
 		auto parentType = parseType(context, domain);
-		parentType = ast::deepCopy(parentType);
 
 		for (size_t i = inheritanceIndex; i < variableDeclarations.size(); i++)
 			variableDeclarations[i]->type = ast::deepCopy(parentType);
 
 		// All types up to now are labeled with their parent types
-		inheritanceIndex = variableDeclarations.size() + 1;
+		inheritanceIndex = variableDeclarations.size();
 
 		tokenizer.skipWhiteSpace();
 	}
diff --git a/lib/pddlparse/tests/TestAcceptanceOfOfficialPDDLInstances.cpp b/lib/pddlparse/tests/TestAcceptanceOfOfficialPDDLInstances.cpp
index 4920cb5..f53e24a 100644
--- a/lib/pddlparse/tests/TestAcceptanceOfOfficialPDDLInstances.cpp
+++ b/lib/pddlparse/tests/TestAcceptanceOfOfficialPDDLInstances.cpp
@@ -7,13 +7,14 @@
 
 namespace fs = std::experimental::filesystem;
 
+const pddl::Context::WarningCallback ignoreWarnings = [](const auto &, const auto &){};
+const auto pddlInstanceBasePath = fs::path("data") / "pddl-instances";
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-TEST_CASE("[PDDL parser acceptance] All the IPC domains are parsed without errors", "[PDDL parser acceptance]")
+TEST_CASE("[PDDL parser acceptance] All official PDDL domains are parsed without errors", "[PDDL parser acceptance]")
 {
-	const pddl::Context::WarningCallback ignoreWarnings = [](const auto &, const auto &){};
-
-	for (const auto &competitionDirectory : fs::directory_iterator("data/pddl-instances"))
+	for (const auto &competitionDirectory : fs::directory_iterator(pddlInstanceBasePath))
 	{
 		if (!fs::is_directory(competitionDirectory))
 			continue;
@@ -36,11 +37,9 @@ TEST_CASE("[PDDL parser acceptance] All the IPC domains are parsed without error
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-TEST_CASE("[PDDL parser acceptance] The first instance of every IPC domain is parsed without errors", "[PDDL parser acceptance]")
+TEST_CASE("[PDDL parser acceptance] The first instance for all official PDDL domains is parsed without errors", "[PDDL parser acceptance]")
 {
-	const pddl::Context::WarningCallback ignoreWarnings = [](const auto &, const auto &){};
-
-	for (const auto &competitionDirectory : fs::directory_iterator("data/pddl-instances"))
+	for (const auto &competitionDirectory : fs::directory_iterator(pddlInstanceBasePath))
 	{
 		if (!fs::is_directory(competitionDirectory))
 			continue;
diff --git a/lib/pddlparse/tests/TestOfficialPDDLInstances.cpp b/lib/pddlparse/tests/TestOfficialPDDLInstances.cpp
new file mode 100644
index 0000000..4d68c1e
--- /dev/null
+++ b/lib/pddlparse/tests/TestOfficialPDDLInstances.cpp
@@ -0,0 +1,40 @@
+#include <catch.hpp>
+
+#include <experimental/filesystem>
+
+#include <pddlparse/AST.h>
+#include <pddlparse/Parse.h>
+
+namespace fs = std::experimental::filesystem;
+
+const pddl::Context::WarningCallback ignoreWarnings = [](const auto &, const auto &){};
+const auto pddlInstanceBasePath = fs::path("data") / "pddl-instances";
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+TEST_CASE("[PDDL parser] The official PDDL instances are parsed correctly", "[PDDL parser]")
+{
+	std::cout << std::endl;
+
+	pddl::Tokenizer tokenizer;
+	pddl::Context context(std::move(tokenizer), ignoreWarnings);
+
+	SECTION("“either” type in zenotravel domain")
+	{
+		const auto domainFile = pddlInstanceBasePath / "ipc-2002" / "domains" / "zenotravel-numeric-hand-coded" / "domain.pddl";
+		context.tokenizer.read(domainFile);
+		auto description = pddl::parseDescription(context);
+
+		const auto &predicates = description.domain->predicates;
+
+		REQUIRE(predicates.size() == 2);
+		REQUIRE(predicates[0]->name == "at");
+		REQUIRE(predicates[0]->parameters.size() == 2);
+		REQUIRE(predicates[0]->parameters[0]->name == "x");
+		REQUIRE(predicates[0]->parameters[0]->type);
+		CHECK(predicates[0]->parameters[0]->type.value().is<pddl::ast::EitherPointer<pddl::ast::PrimitiveTypePointer>>());
+		REQUIRE(predicates[0]->parameters[1]->name == "c");
+		REQUIRE(predicates[0]->parameters[1]->type);
+		CHECK(predicates[0]->parameters[1]->type.value().is<pddl::ast::PrimitiveTypePointer>());
+	}
+}