diff --git a/src/utility/shortestPaths.cpp b/src/utility/shortestPaths.cpp
index c9ce0b608..8d1dd079f 100644
--- a/src/utility/shortestPaths.cpp
+++ b/src/utility/shortestPaths.cpp
@@ -7,7 +7,7 @@ namespace storm {
     namespace utility {
         namespace ksp {
             template <typename T>
-            ShortestPathsGenerator<T>::ShortestPathsGenerator(storage::SparseMatrix<T> transitionMatrix, std::unordered_map<state_t, T> targetProbMap, BitVector initialStates) :
+            ShortestPathsGenerator<T>::ShortestPathsGenerator(storage::SparseMatrix<T> const& transitionMatrix, std::unordered_map<state_t, T> const& targetProbMap, BitVector const& initialStates) :
                     transitionMatrix(transitionMatrix),
                     numStates(transitionMatrix.getColumnCount() + 1), // one more for meta-target
                     metaTarget(transitionMatrix.getColumnCount()), // first unused state index
@@ -28,7 +28,7 @@ namespace storm {
             }
 
             template <typename T>
-            ShortestPathsGenerator<T>::ShortestPathsGenerator(storage::SparseMatrix<T> transitionMatrix, std::vector<T> targetProbVector, BitVector initialStates)
+            ShortestPathsGenerator<T>::ShortestPathsGenerator(storage::SparseMatrix<T> const& transitionMatrix, std::vector<T> const& targetProbVector, BitVector const& initialStates)
                     : ShortestPathsGenerator<T>(transitionMatrix, vectorToMap(targetProbVector), initialStates) {}
 
             // extracts the relevant info from the model and delegates to ctor above
diff --git a/src/utility/shortestPaths.h b/src/utility/shortestPaths.h
index 1cda2eb99..67e857e5d 100644
--- a/src/utility/shortestPaths.h
+++ b/src/utility/shortestPaths.h
@@ -67,8 +67,8 @@ namespace storm {
                 // a further alternative: use transition matrix of maybe-states
                 // combined with target vector (e.g., the instantiated matrix/vector from SamplingModel);
                 // in this case separately specifying a target makes no sense
-                ShortestPathsGenerator(storage::SparseMatrix<T> transitionMatrix, std::vector<T> targetProbVector, BitVector initialStates);
-                ShortestPathsGenerator(storage::SparseMatrix<T> maybeTransitionMatrix, std::unordered_map<state_t, T> targetProbMap, BitVector initialStates);
+                ShortestPathsGenerator(storage::SparseMatrix<T> const& transitionMatrix, std::vector<T> const& targetProbVector, BitVector const& initialStates);
+                ShortestPathsGenerator(storage::SparseMatrix<T> const& maybeTransitionMatrix, std::unordered_map<state_t, T> const& targetProbMap, BitVector const& initialStates);
 
 
                 inline ~ShortestPathsGenerator(){}
@@ -97,7 +97,7 @@ namespace storm {
 
 
             private:
-                storage::SparseMatrix<T> transitionMatrix;
+                storage::SparseMatrix<T> const& transitionMatrix; // FIXME: store reference instead (?)
                 state_t numStates; // includes meta-target, i.e. states in model + 1
                 state_t metaTarget;
                 BitVector initialStates;