diff --git a/include/plasp/pddl/Domain.h b/include/plasp/pddl/Domain.h
index 7f4eb46..d9261ca 100644
--- a/include/plasp/pddl/Domain.h
+++ b/include/plasp/pddl/Domain.h
@@ -33,6 +33,7 @@ class Domain
 
 		const Requirements &requirements() const;
 		bool hasRequirement(Requirement::Type requirementType) const;
+		void checkRequirement(Requirement::Type requirementType) const;
 
 		expressions::PrimitiveTypes &types();
 		const expressions::PrimitiveTypes &types() const;
diff --git a/include/plasp/pddl/Problem.h b/include/plasp/pddl/Problem.h
index 4ffb2ce..c360b5b 100644
--- a/include/plasp/pddl/Problem.h
+++ b/include/plasp/pddl/Problem.h
@@ -32,6 +32,7 @@ class Problem
 
 		const Requirements &requirements() const;
 		bool hasRequirement(Requirement::Type requirementType) const;
+		void checkRequirement(Requirement::Type requirementType) const;
 
 		expressions::Constants &objects();
 		const expressions::Constants &objects() const;
diff --git a/include/plasp/pddl/Requirement.h b/include/plasp/pddl/Requirement.h
index 45106ab..266b5ba 100644
--- a/include/plasp/pddl/Requirement.h
+++ b/include/plasp/pddl/Requirement.h
@@ -56,8 +56,8 @@ class Requirement
 
 		Type type() const;
 
-		void printAsPDDL(std::ostream &ostream) const;
-		void printAsASP(std::ostream &ostream) const;
+		std::string toPDDL() const;
+		std::string toASP() const;
 
 	private:
 		Type m_type;
diff --git a/src/plasp/pddl/Domain.cpp b/src/plasp/pddl/Domain.cpp
index d6e1e7e..d351e39 100644
--- a/src/plasp/pddl/Domain.cpp
+++ b/src/plasp/pddl/Domain.cpp
@@ -206,6 +206,16 @@ bool Domain::hasRequirement(Requirement::Type requirementType) const
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+void Domain::checkRequirement(Requirement::Type requirementType) const
+{
+	if (hasRequirement(requirementType))
+		return;
+
+	throw ConsistencyException("Requirement \"" + Requirement(requirementType).toPDDL() + "\" used but never declared");
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 void Domain::computeDerivedRequirements()
 {
 	const auto addRequirementUnique =
diff --git a/src/plasp/pddl/Problem.cpp b/src/plasp/pddl/Problem.cpp
index c0b0d65..632c099 100644
--- a/src/plasp/pddl/Problem.cpp
+++ b/src/plasp/pddl/Problem.cpp
@@ -190,6 +190,18 @@ bool Problem::hasRequirement(Requirement::Type requirementType) const
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+void Problem::checkRequirement(Requirement::Type requirementType) const
+{
+	m_domain.checkRequirement(requirementType);
+
+	if (hasRequirement(requirementType))
+		return;
+
+	throw ConsistencyException("Requirement \"" + Requirement(requirementType).toPDDL() + "\" used but never declared");
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 void Problem::computeDerivedRequirements()
 {
 	const auto addRequirementUnique =
diff --git a/src/plasp/pddl/Requirement.cpp b/src/plasp/pddl/Requirement.cpp
index 451ee0f..38f94c9 100644
--- a/src/plasp/pddl/Requirement.cpp
+++ b/src/plasp/pddl/Requirement.cpp
@@ -101,24 +101,24 @@ Requirement::Type Requirement::type() const
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-void Requirement::printAsPDDL(std::ostream &ostream) const
+std::string Requirement::toPDDL() const
 {
 	const auto match = requirementTypesToPDDL.left.find(m_type);
 
 	BOOST_ASSERT(match != requirementTypesToPDDL.left.end());
 
-	ostream << match->second;
+	return match->second;
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-void Requirement::printAsASP(std::ostream &ostream) const
+std::string Requirement::toASP() const
 {
 	const auto match = requirementTypesToASP.left.find(m_type);
 
 	BOOST_ASSERT(match != requirementTypesToASP.left.end());
 
-	ostream << match->second;
+	return match->second;
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////