diff --git a/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.hpp b/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.hpp
index 200888b4..939d0ba1 100644
--- a/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.hpp
+++ b/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.hpp
@@ -74,12 +74,12 @@ class ram_pcd_message : public r1cs_pcd_message<ram_base_field<ramT> > {
     ram_pcd_message(const size_t type,
                     const ram_architecture_params<ramT> &ap,
                     const size_t timestamp,
-                    const libff::bit_vector root_initial,
-                    const libff::bit_vector root,
+                    const libff::bit_vector &root_initial,
+                    const libff::bit_vector &root,
                     const size_t pc_addr,
-                    const libff::bit_vector cpu_state,
+                    const libff::bit_vector &cpu_state,
                     const size_t pc_addr_initial,
-                    const libff::bit_vector cpu_state_initial,
+                    const libff::bit_vector &cpu_state_initial,
                     const bool has_accepted);
 
     libff::bit_vector unpacked_payload_as_bits() const;
diff --git a/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.tcc b/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.tcc
index 1be6ffde..f0329caa 100644
--- a/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.tcc
+++ b/libsnark/zk_proof_systems/zksnark/ram_zksnark/ram_compliance_predicate.tcc
@@ -22,12 +22,12 @@ template<typename ramT>
 ram_pcd_message<ramT>::ram_pcd_message(const size_t type,
                                        const ram_architecture_params<ramT> &ap,
                                        const size_t timestamp,
-                                       const libff::bit_vector root_initial,
-                                       const libff::bit_vector root,
+                                       const libff::bit_vector &root_initial,
+                                       const libff::bit_vector &root,
                                        const size_t pc_addr,
-                                       const libff::bit_vector cpu_state,
+                                       const libff::bit_vector &cpu_state,
                                        const size_t pc_addr_initial,
-                                       const libff::bit_vector cpu_state_initial,
+                                       const libff::bit_vector &cpu_state_initial,
                                        const bool has_accepted) :
     r1cs_pcd_message<FieldT>(type),
     ap(ap),