diff --git a/include/loki/common/collections.hpp b/include/loki/common/collections.hpp
index 7ff26cad..100ca236 100644
--- a/include/loki/common/collections.hpp
+++ b/include/loki/common/collections.hpp
@@ -31,8 +31,8 @@ namespace loki {
 /// @param vec
 /// @return
 template<typename Collection>
-std::vector<typename Collection::value_type> get_sorted_vector(const Collection& collection) {
-    std::vector<typename Collection::value_type> result(collection.begin(), collection.end());
+boost::container::small_vector<typename Collection::value_type, 100> get_sorted_vector(const Collection& collection) {
+    boost::container::small_vector<typename Collection::value_type, 100> result(collection.begin(), collection.end());
     std::sort(result.begin(), result.end());
     return result;
 }
diff --git a/include/loki/common/pddl/garbage_collected_factory.hpp b/include/loki/common/pddl/garbage_collected_factory.hpp
index 5aca59ed..6f82196e 100644
--- a/include/loki/common/pddl/garbage_collected_factory.hpp
+++ b/include/loki/common/pddl/garbage_collected_factory.hpp
@@ -75,7 +75,7 @@ class GarbageCollectedFactory {
         auto& t_cache = std::get<PerTypeCache<T>>(m_cache->data);
         int identifier = m_cache->count;
         auto key = T(identifier, args...);
-        const auto& [it, inserted] = t_cache.uniqueness.insert(key);
+        const auto [it, inserted] = t_cache.uniqueness.insert(key);
         if (!inserted) {
             assert(t_cache.identifier_to_object.count(it->get_identifier()));
             return t_cache.identifier_to_object.at(it->get_identifier()).lock();
diff --git a/include/loki/common/pddl/persistent_factory.hpp b/include/loki/common/pddl/persistent_factory.hpp
index 78810cf0..c82482db 100644
--- a/include/loki/common/pddl/persistent_factory.hpp
+++ b/include/loki/common/pddl/persistent_factory.hpp
@@ -68,7 +68,7 @@ class PersistentFactory {
     /// @brief Returns a pointer to an existing object
     ///        or creates it before if it does not exist.v
     template<typename SubType, typename... Args>
-    [[nodiscard]] HolderType const* get_or_create(Args... args) {
+    [[nodiscard]] HolderType const* get_or_create(Args&&... args) {
         std::lock_guard<std::mutex> hold(m_mutex);
         /* Construct and insert the element in persistent memory. */
         size_t identifier = m_count;
@@ -76,26 +76,18 @@ class PersistentFactory {
         assert((identifier == (m_persistent_vector.size()-1))
             || (identifier == m_persistent_vector.size()));
         // Explicitly call the constructor of T to give exclusive access to the factory.
-        auto element = HolderType(std::move(SubType(identifier, args...)));
+        auto element = HolderType(std::move(SubType(identifier, std::forward<Args>(args)...)));
         bool overwrite_last_element = (identifier == m_persistent_vector.size() - 1);
         // The pointer to the location in persistent memory.
-        const auto* element_ptr = static_cast<const HolderType*>(nullptr);
-        if (overwrite_last_element) {
-            const auto& persistent_element = m_persistent_vector[identifier] = std::move(element);
-            element_ptr = &persistent_element;
-        } else {
-            const auto& persistent_element = m_persistent_vector.push_back(std::move(element));
-            element_ptr = &persistent_element;
-        }
-        if (!element_ptr) {
-            throw std::runtime_error("element_ptr is nullptr");
-        }
+        const auto* element_ptr = overwrite_last_element 
+            ? &(m_persistent_vector[identifier] = std::move(element))
+            : &(m_persistent_vector.push_back(std::move(element)));
         assert(element_ptr);
         /* Test for uniqueness */
         auto it = m_uniqueness_set.find(element_ptr);
         if (it == m_uniqueness_set.end()) {
             // Element is unique! 
-            m_uniqueness_set.insert(element_ptr);
+            m_uniqueness_set.emplace(element_ptr);
             // Validate the element by increasing the identifier to the next free position
             ++m_count;
             assert(m_uniqueness_set.size() == m_count);
diff --git a/include/loki/domain/pddl/declarations.hpp b/include/loki/domain/pddl/declarations.hpp
index ad71d5b6..1ac23faa 100644
--- a/include/loki/domain/pddl/declarations.hpp
+++ b/include/loki/domain/pddl/declarations.hpp
@@ -33,8 +33,8 @@ namespace loki::pddl {
 
     class TypeImpl;
     using Type = const TypeImpl*;
-    //using TypeList = boost::container::small_vector<Type,1>;  // often single type
-    using TypeList = std::vector<Type>;
+    using TypeList = boost::container::small_vector<Type,1>;  // often single type
+    //using TypeList = std::vector<Type>;
 
     class ObjectImpl;
     using Object = const ObjectImpl*;
@@ -49,8 +49,8 @@ namespace loki::pddl {
     class TermVariableImpl;
     using TermImpl = std::variant<TermObjectImpl, TermVariableImpl>;
     using Term = const TermImpl*;
-    //using TermList = boost::container::small_vector<Term, 2>;  // often unary and binary predicates
-    using TermList = std::vector<Term>;
+    using TermList = boost::container::small_vector<Term, 2>;  // often unary and binary predicates
+    //using TermList = std::vector<Term>;
 
     class AtomImpl;
     using Atom = const AtomImpl*;
@@ -58,8 +58,8 @@ namespace loki::pddl {
 
     class ParameterImpl;
     using Parameter = const ParameterImpl*;
-    //using ParameterList = boost::container::small_vector<Parameter, 10>;  // often actions, quantifiers with few parameters
-    using ParameterList = std::vector<Parameter>;
+    using ParameterList = boost::container::small_vector<Parameter, 10>;  // often actions, quantifiers with few parameters
+    //using ParameterList = std::vector<Parameter>;
     using ParameterAssignment = std::unordered_map<Parameter, Object>;
 
     class PredicateImpl;
diff --git a/include/loki/domain/pddl/object.hpp b/include/loki/domain/pddl/object.hpp
index d9fb6598..9db15e17 100644
--- a/include/loki/domain/pddl/object.hpp
+++ b/include/loki/domain/pddl/object.hpp
@@ -37,7 +37,7 @@ class ObjectImpl : public Base<ObjectImpl> {
     std::string m_name;
     TypeList m_types;
 
-    ObjectImpl(int identifier, std::string name, TypeList types);
+    ObjectImpl(int identifier, std::string name, TypeList types={});
 
     // Give access to the constructor.
     template<typename HolderType, ElementsPerSegment N>
diff --git a/include/loki/domain/pddl/type.hpp b/include/loki/domain/pddl/type.hpp
index 3da5e7bd..b4eda99b 100644
--- a/include/loki/domain/pddl/type.hpp
+++ b/include/loki/domain/pddl/type.hpp
@@ -37,7 +37,7 @@ class TypeImpl : public Base<TypeImpl> {
     std::string m_name;
     TypeList m_bases;
 
-    TypeImpl(int identifier, std::string name, TypeList bases);
+    TypeImpl(int identifier, std::string name, TypeList bases = {});
 
     // Give access to the constructor.
     template<typename HolderType, ElementsPerSegment N>
diff --git a/src/domain/pddl/parser/common.cpp b/src/domain/pddl/parser/common.cpp
index 693cd241..e9e1b6a9 100644
--- a/src/domain/pddl/parser/common.cpp
+++ b/src/domain/pddl/parser/common.cpp
@@ -54,7 +54,7 @@ pddl::Term TermDeclarationTermVisitor::operator()(const ast::Name& node) const {
     }
     // Constant are not tracked and hence must not be untracked.
     // Construct Term and return it
-    const auto& [constant, _position, _error_handler] = binding.value();
+    const auto [constant, _position, _error_handler] = binding.value();
     const auto term = context.factories.terms.get_or_create<pddl::TermObjectImpl>(constant);
     // Add position of PDDL object
     context.positions.push_back(term, node);
@@ -68,7 +68,7 @@ pddl::Term TermDeclarationTermVisitor::operator()(const ast::Variable& node) con
     const auto binding = context.scopes.get<pddl::VariableImpl>(variable->get_name());
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
-        const auto& [_constant, position, error_handler] = binding.value();
+        const auto [_constant, position, error_handler] = binding.value();
         assert(position.has_value());
         const auto message_2 = error_handler(position.value(), "First defined here:");
         throw MultiDefinitionVariableError(variable->get_name(), message_1 + message_2);
@@ -94,7 +94,7 @@ pddl::Term TermReferenceTermVisitor::operator()(const ast::Name& node) const {
         throw UndefinedConstantError(object_name, context.scopes.get_error_handler()(node, ""));
     }
     // Construct Term and return it
-    const auto& [object, _position, _error_handler] = binding.value();
+    const auto [object, _position, _error_handler] = binding.value();
     context.references.untrack(object);
     const auto term = context.factories.terms.get_or_create<pddl::TermObjectImpl>(object);
     // Add position of PDDL object
diff --git a/src/domain/pddl/parser/constants.cpp b/src/domain/pddl/parser/constants.cpp
index 70fa95a8..982b64d9 100644
--- a/src/domain/pddl/parser/constants.cpp
+++ b/src/domain/pddl/parser/constants.cpp
@@ -33,7 +33,7 @@ static void test_multiple_definition(const pddl::Object& constant, const domain:
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_object, position, error_handler] = binding.value();
+        const auto [_object, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
@@ -78,8 +78,7 @@ pddl::ObjectList ConstantListVisitor::operator()(const std::vector<ast::Name>& n
     // std::vector<ast::Name> has single base type "object"
     assert(context.scopes.get<pddl::TypeImpl>("object").has_value());
     const auto [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("object").value();
-    const auto type_list = pddl::TypeList{type};
-    return parse_constant_definitions(name_nodes, type_list, context);
+    return parse_constant_definitions(name_nodes, pddl::TypeList{type}, context);
 }
 
 pddl::ObjectList ConstantListVisitor::operator()(const ast::TypedListOfNamesRecursively& typed_list_of_names_recursively_node) {
diff --git a/src/domain/pddl/parser/effects.cpp b/src/domain/pddl/parser/effects.cpp
index b79c2062..d9ad2b6d 100644
--- a/src/domain/pddl/parser/effects.cpp
+++ b/src/domain/pddl/parser/effects.cpp
@@ -85,7 +85,7 @@ pddl::Effect parse(const domain::ast::EffectProductionNumericFluentTotalCost& no
     if (!binding.has_value()) {
         throw UndefinedFunctionSkeletonError(function_name, context.scopes.get_error_handler()(node.function_symbol_total_cost, ""));
     }
-    const auto& [function_skeleton, _position, _error_handler] = binding.value();
+    const auto [function_skeleton, _position, _error_handler] = binding.value();
     const auto function = context.factories.functions.get_or_create<pddl::FunctionImpl>(function_skeleton, pddl::TermList{});
     context.references.untrack(function->get_function_skeleton());
     const auto function_expression = boost::apply_visitor(FunctionExpressionVisitor(context), node.numeric_term);
diff --git a/src/domain/pddl/parser/functions.cpp b/src/domain/pddl/parser/functions.cpp
index 9a14466d..e06d0f99 100644
--- a/src/domain/pddl/parser/functions.cpp
+++ b/src/domain/pddl/parser/functions.cpp
@@ -121,7 +121,7 @@ pddl::FunctionSkeleton parse_function_skeleton_reference(const domain::ast::Func
     if (!binding.has_value()) {
         throw UndefinedFunctionSkeletonError(function_name, context.scopes.get_error_handler()(node, ""));
     }
-    const auto& [function_skeleton, _position, _error_handler] = binding.value();
+    const auto [function_skeleton, _position, _error_handler] = binding.value();
     context.references.untrack(function_skeleton);
     return function_skeleton;
 }
@@ -133,7 +133,7 @@ static void test_multiple_definition(const pddl::FunctionSkeleton& function_skel
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_function_skeleton, position, error_handler] = binding.value();
+        const auto [_function_skeleton, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
@@ -163,7 +163,7 @@ pddl::FunctionSkeleton parse(const domain::ast::AtomicFunctionSkeletonTotalCost&
     }
 
     assert(context.scopes.get<pddl::TypeImpl>("number").has_value());
-    const auto& [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("number").value();
+    const auto [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("number").value();
     auto function_name = parse(node.function_symbol.name);
     auto function_skeleton = context.factories.function_skeletons.get_or_create<pddl::FunctionSkeletonImpl>(function_name, pddl::ParameterList{}, type);
 
@@ -184,7 +184,7 @@ pddl::FunctionSkeleton parse(const domain::ast::AtomicFunctionSkeletonGeneral& n
     context.scopes.close_scope();
 
     assert(context.scopes.get<pddl::TypeImpl>("number").has_value());
-    const auto& [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("number").value();
+    const auto [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("number").value();
     auto function_name = parse(node.function_symbol.name);
     auto function_skeleton = context.factories.function_skeletons.get_or_create<pddl::FunctionSkeletonImpl>(function_name, function_parameters, type);
 
diff --git a/src/domain/pddl/parser/literal.cpp b/src/domain/pddl/parser/literal.cpp
index c8530ce5..683af764 100644
--- a/src/domain/pddl/parser/literal.cpp
+++ b/src/domain/pddl/parser/literal.cpp
@@ -33,7 +33,7 @@ pddl::Atom parse(const domain::ast::AtomicFormulaOfTermsPredicate& node, Context
     for (const auto& term_node : node.terms) {
         term_list.push_back(boost::apply_visitor(TermReferenceTermVisitor(context), term_node));
     }
-    const auto& [predicate, _position, _error_handler] = binding.value();
+    const auto [predicate, _position, _error_handler] = binding.value();
     if (predicate->get_parameters().size() != term_list.size()) {
         throw MismatchedPredicateTermListError(predicate, term_list, context.scopes.get_error_handler()(node, ""));
     }
@@ -50,7 +50,7 @@ pddl::Atom parse(const domain::ast::AtomicFormulaOfTermsEquality& node, Context&
     }
     context.references.untrack(pddl::RequirementEnum::EQUALITY);
     assert(context.scopes.get<pddl::PredicateImpl>("=").has_value());
-    const auto& [equal_predicate, _position, _error_handler] = context.scopes.get<pddl::PredicateImpl>("=").value();
+    const auto [equal_predicate, _position, _error_handler] = context.scopes.get<pddl::PredicateImpl>("=").value();
     auto left_term = boost::apply_visitor(TermReferenceTermVisitor(context), node.term_left);
     auto right_term = boost::apply_visitor(TermReferenceTermVisitor(context), node.term_right);
     const auto atom = context.factories.atoms.get_or_create<pddl::AtomImpl>(
diff --git a/src/domain/pddl/parser/parameters.cpp b/src/domain/pddl/parser/parameters.cpp
index 3a2ee9c9..402cdb96 100644
--- a/src/domain/pddl/parser/parameters.cpp
+++ b/src/domain/pddl/parser/parameters.cpp
@@ -33,7 +33,7 @@ static void test_multiple_definition(const pddl::Variable& variable, const ast::
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_variable, position, error_handler] = binding.value();
+        const auto [_variable, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
diff --git a/src/domain/pddl/parser/predicates.cpp b/src/domain/pddl/parser/predicates.cpp
index cceea1a5..989d04f1 100644
--- a/src/domain/pddl/parser/predicates.cpp
+++ b/src/domain/pddl/parser/predicates.cpp
@@ -30,7 +30,7 @@ static void test_multiple_definition(const pddl::Predicate& predicate, const dom
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_predicate, position, error_handler] = binding.value();
+        const auto [_predicate, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
diff --git a/src/domain/pddl/parser/reference_utils.cpp b/src/domain/pddl/parser/reference_utils.cpp
index 19a9c5a4..b68936c6 100644
--- a/src/domain/pddl/parser/reference_utils.cpp
+++ b/src/domain/pddl/parser/reference_utils.cpp
@@ -31,7 +31,7 @@ void track_variable_references(const pddl::ParameterList& parameter_list, Contex
 void test_variable_references(const pddl::ParameterList& parameter_list, const Context& context) {
     for (const auto& parameter : parameter_list) {
         if (context.references.exists(parameter->get_variable())) {
-            const auto& [variable, position, error_handler] = context.scopes.get<pddl::VariableImpl>(parameter->get_variable()->get_name()).value();
+            const auto [variable, position, error_handler] = context.scopes.get<pddl::VariableImpl>(parameter->get_variable()->get_name()).value();
             throw UnusedVariableError(variable->get_name(), error_handler(position.value(), ""));
         }
     }
@@ -47,7 +47,7 @@ void track_predicate_references(const pddl::PredicateList& predicate_list, Conte
 void test_predicate_references(const pddl::PredicateList& predicate_list, const Context& context) {
     for (const auto& predicate : predicate_list) {
         if (context.references.exists(predicate)) {
-            const auto& [_predicate, position, error_handler] = context.scopes.get<pddl::PredicateImpl>(predicate->get_name()).value();
+            const auto [_predicate, position, error_handler] = context.scopes.get<pddl::PredicateImpl>(predicate->get_name()).value();
             throw UnusedPredicateError(predicate->get_name(), error_handler(position.value(), ""));
         }
     }
@@ -63,7 +63,7 @@ void track_function_skeleton_references(const pddl::FunctionSkeletonList& functi
 void test_function_skeleton_references(const pddl::FunctionSkeletonList& function_skeleton_list, const Context& context) {
     for (const auto& function_skeleton : function_skeleton_list) {
         if (context.references.exists(function_skeleton)) {
-            const auto& [_function_skeleton, position, error_handler] = context.scopes.get<pddl::FunctionSkeletonImpl>(function_skeleton->get_name()).value();
+            const auto [_function_skeleton, position, error_handler] = context.scopes.get<pddl::FunctionSkeletonImpl>(function_skeleton->get_name()).value();
             throw UnusedFunctionSkeletonError(function_skeleton->get_name(), error_handler(position.value(), ""));
         }
     }
diff --git a/src/domain/pddl/parser/types.cpp b/src/domain/pddl/parser/types.cpp
index 8f8ac0ba..c1a5c8fb 100644
--- a/src/domain/pddl/parser/types.cpp
+++ b/src/domain/pddl/parser/types.cpp
@@ -68,14 +68,14 @@ TypeReferenceTypeVisitor::TypeReferenceTypeVisitor(const Context& context_)
 pddl::TypeList TypeReferenceTypeVisitor::operator()(const ast::TypeObject&) {
     const auto binding = context.scopes.get<pddl::TypeImpl>("object");
     assert(binding.has_value());
-    const auto& [type, _position, _error_handler] = binding.value();
+    const auto [type, _position, _error_handler] = binding.value();
     return {type};
 }
 
 pddl::TypeList TypeReferenceTypeVisitor::operator()(const ast::TypeNumber&) {
     const auto binding = context.scopes.get<pddl::TypeImpl>("number");
     assert(binding.has_value());
-    const auto& [type, _position, _error_handler] = binding.value();
+    const auto [type, _position, _error_handler] = binding.value();
     return {type};
 }
 
@@ -85,7 +85,7 @@ pddl::TypeList TypeReferenceTypeVisitor::operator()(const domain::ast::Name& nod
     if (!binding.has_value()) {
         throw UndefinedTypeError(name, context.scopes.get_error_handler()(node, ""));
     }
-    const auto& [type, _position, _error_handler] = binding.value();
+    const auto [type, _position, _error_handler] = binding.value();
     context.positions.push_back(type, node);
     return { type };
 }
@@ -107,7 +107,7 @@ static void test_multiple_definition(const pddl::Type& type, const domain::ast::
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_type, position, error_handler] = binding.value();
+        const auto [_type, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
@@ -159,9 +159,8 @@ TypeDeclarationTypedListOfNamesVisitor::TypeDeclarationTypedListOfNamesVisitor(C
 pddl::TypeList TypeDeclarationTypedListOfNamesVisitor::operator()(const std::vector<domain::ast::Name>& name_nodes) {
     // std::vector<domain::ast::Name> has single base type "object"
     assert(context.scopes.get<pddl::TypeImpl>("object").has_value());
-    const auto& [type_object, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("object").value();
-    const auto base_types = pddl::TypeList{type_object};
-    const auto type_list = parse_type_definitions(name_nodes, base_types, context);
+    const auto [type_object, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("object").value();
+    const auto type_list = parse_type_definitions(name_nodes, pddl::TypeList{type_object}, context);
     return type_list;
 }
 
diff --git a/src/problem/pddl/parser/literal.cpp b/src/problem/pddl/parser/literal.cpp
index 3cbc4fca..ef7084c7 100644
--- a/src/problem/pddl/parser/literal.cpp
+++ b/src/problem/pddl/parser/literal.cpp
@@ -38,7 +38,7 @@ pddl::GroundAtom parse(const problem::ast::AtomicFormulaOfNamesPredicate& node,
     for (const auto& name_node : node.names) {
         object_list.push_back(parse_object_reference(name_node, context));
     }
-    const auto& [predicate, _position, _error_handler] = binding.value();
+    const auto [predicate, _position, _error_handler] = binding.value();
     if (predicate->get_parameters().size() != object_list.size()) {
         throw MismatchedPredicateObjectListError(predicate, object_list, context.scopes.get_error_handler()(node, ""));
     }
@@ -52,7 +52,7 @@ pddl::GroundAtom parse(const problem::ast::AtomicFormulaOfNamesEquality& node, C
         throw UndefinedRequirementError(pddl::RequirementEnum::EQUALITY, context.scopes.get_error_handler()(node, ""));
     }
     assert(context.scopes.get<pddl::PredicateImpl>("=").has_value());
-    const auto& [equal_predicate, _position, _error_handler] = context.scopes.get<pddl::PredicateImpl>("=").value();
+    const auto [equal_predicate, _position, _error_handler] = context.scopes.get<pddl::PredicateImpl>("=").value();
     const auto object_left = parse_object_reference(node.name_left, context);
     const auto object_right = parse_object_reference(node.name_right, context);
     const auto atom = context.factories.ground_atoms.get_or_create<pddl::GroundAtomImpl>(equal_predicate, pddl::ObjectList{object_left, object_right});
diff --git a/src/problem/pddl/parser/objects.cpp b/src/problem/pddl/parser/objects.cpp
index e928090f..3303f624 100644
--- a/src/problem/pddl/parser/objects.cpp
+++ b/src/problem/pddl/parser/objects.cpp
@@ -40,7 +40,7 @@ pddl::Object parse_object_reference(const domain::ast::Name& name_node, Context&
     if (!binding.has_value()) {
         throw UndefinedObjectError(name, context.scopes.get_error_handler()(name_node, ""));
     }
-    const auto& [object, _position, _error_handler] = binding.value();
+    const auto [object, _position, _error_handler] = binding.value();
     context.positions.push_back(object, name_node);
     context.references.untrack(object);
     return object;
@@ -52,7 +52,7 @@ static void test_multiple_definition_object(const std::string& object_name, cons
     if (binding.has_value()) {
         const auto message_1 = context.scopes.get_error_handler()(name_node, "Defined here:");
         auto message_2 = std::string("");
-        const auto& [_object, position, error_handler] = binding.value();
+        const auto [_object, position, error_handler] = binding.value();
         if (position.has_value()) {
             message_2 = error_handler(position.value(), "First defined here:");
         }
@@ -83,7 +83,7 @@ static pddl::ObjectList parse_object_definitions(const std::vector<domain::ast::
 pddl::ObjectList ObjectListVisitor::operator()(const std::vector<domain::ast::Name>& name_nodes) {
     // std::vector<domain::ast::Name> has single base type "object"
     assert(context.scopes.get<pddl::TypeImpl>("object").has_value());
-    const auto& [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("object").value();
+    const auto [type, _position, _error_handler] = context.scopes.get<pddl::TypeImpl>("object").value();
     auto object_list = parse_object_definitions(name_nodes, pddl::TypeList{type}, context);
     return object_list;
 }
diff --git a/src/problem/pddl/parser/reference_utils.cpp b/src/problem/pddl/parser/reference_utils.cpp
index a10c4415..a0cc761f 100644
--- a/src/problem/pddl/parser/reference_utils.cpp
+++ b/src/problem/pddl/parser/reference_utils.cpp
@@ -31,7 +31,7 @@ void track_object_references(const pddl::ObjectList& object_list, Context& conte
 void test_object_references(const pddl::ObjectList& object_list, const Context& context) {
     for (const auto& object : object_list) {
         if (context.references.exists(object)) {
-            const auto& [_object, position, error_handler] = context.scopes.get<pddl::ObjectImpl>(object->get_name()).value();
+            const auto [_object, position, error_handler] = context.scopes.get<pddl::ObjectImpl>(object->get_name()).value();
             throw UnusedObjectError(object->get_name(), error_handler(position.value(), ""));
         }
     }