diff --git a/include/plasp/pddl/expressions/DerivedPredicate.h b/include/plasp/pddl/expressions/DerivedPredicate.h
index 53087f7..3bc3765 100644
--- a/include/plasp/pddl/expressions/DerivedPredicate.h
+++ b/include/plasp/pddl/expressions/DerivedPredicate.h
@@ -24,12 +24,18 @@ class DerivedPredicate: public ExpressionCRTP<DerivedPredicate>
 		// TODO: consider implementing parsing functions for compatibility with older PDDL versions
 
 	public:
+		explicit DerivedPredicate(size_t id);
+
+		size_t id() const;
+
 		void setArgument(ExpressionPointer argument);
 		ExpressionPointer argument() const;
 
 		void print(std::ostream &ostream) const override;
 
 	private:
+		size_t m_id;
+
 		ExpressionPointer m_argument;
 };
 
diff --git a/src/plasp/pddl/expressions/DerivedPredicate.cpp b/src/plasp/pddl/expressions/DerivedPredicate.cpp
index c211c9b..cf0d10b 100644
--- a/src/plasp/pddl/expressions/DerivedPredicate.cpp
+++ b/src/plasp/pddl/expressions/DerivedPredicate.cpp
@@ -16,6 +16,20 @@ namespace expressions
 //
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+DerivedPredicate::DerivedPredicate(size_t id)
+:	m_id{id}
+{
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+size_t DerivedPredicate::id() const
+{
+	return m_id;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 void DerivedPredicate::setArgument(ExpressionPointer argument)
 {
 	m_argument = argument;
diff --git a/src/plasp/pddl/expressions/ForAll.cpp b/src/plasp/pddl/expressions/ForAll.cpp
index 4013f7f..6ce8550 100644
--- a/src/plasp/pddl/expressions/ForAll.cpp
+++ b/src/plasp/pddl/expressions/ForAll.cpp
@@ -24,7 +24,7 @@ const std::string ForAll::Identifier = "forall";
 
 ExpressionPointer ForAll::decomposed(DerivedPredicates &derivedPredicates)
 {
-	auto derivedPredicate = DerivedPredicatePointer(new DerivedPredicate);
+	auto derivedPredicate = DerivedPredicatePointer(new DerivedPredicate(derivedPredicates.size()));
 	derivedPredicates.push_back(derivedPredicate);
 
 	derivedPredicate->setArgument(this);
diff --git a/src/plasp/pddl/expressions/Or.cpp b/src/plasp/pddl/expressions/Or.cpp
index 5fbedb3..f7c0293 100644
--- a/src/plasp/pddl/expressions/Or.cpp
+++ b/src/plasp/pddl/expressions/Or.cpp
@@ -28,7 +28,7 @@ ExpressionPointer Or::decomposed(DerivedPredicates &derivedPredicates)
 			argument = argument->decomposed(derivedPredicates);
 		});
 
-	auto derivedPredicate = DerivedPredicatePointer(new DerivedPredicate);
+	auto derivedPredicate = DerivedPredicatePointer(new DerivedPredicate(derivedPredicates.size()));
 	derivedPredicates.push_back(derivedPredicate);
 
 	derivedPredicate->setArgument(this);