diff --git a/corsika/detail/framework/core/ParticleProperties.inl b/corsika/detail/framework/core/ParticleProperties.inl
index 7d0aa253b838adf8a06d5f0cdfbb71022d896695..47504f4ea5f0dd02672418e260eb61dd6971c5c3 100644
--- a/corsika/detail/framework/core/ParticleProperties.inl
+++ b/corsika/detail/framework/core/ParticleProperties.inl
@@ -53,15 +53,15 @@ namespace corsika {
     return particle::detail::isHadron[static_cast<CodeIntType>(p)];
   }
 
-  inline bool constexpr is_em(Code c) {
+  inline bool constexpr is_em(Code const c) {
     return c == Code::Electron || c == Code::Positron || c == Code::Gamma;
   }
 
-  inline bool constexpr is_muon(Code c) {
+  inline bool constexpr is_muon(Code const c) {
     return c == Code::MuPlus || c == Code::MuMinus;
   }
 
-  inline bool constexpr is_neutrino(Code c) {
+  inline bool constexpr is_neutrino(Code const c) {
     return c == Code::NuE || c == Code::NuMu || c == Code::NuTau || c == Code::NuEBar ||
            c == Code::NuMuBar || c == Code::NuTauBar;
   }
@@ -88,7 +88,7 @@ namespace corsika {
     return stream << get_name(code);
   }
 
-  inline Code convert_from_PDG(PDGCode p) {
+  inline Code convert_from_PDG(PDGCode const p) {
     static_assert(particle::detail::conversionArray.size() % 2 == 1);
     // this will fail, for the strange case where the maxPDG is negative...
     int constexpr maxPDG{(particle::detail::conversionArray.size() - 1) >> 1};
diff --git a/corsika/framework/core/ParticleProperties.hpp b/corsika/framework/core/ParticleProperties.hpp
index dafc1f02437fcecc0c926b9b9b94a283997c03b6..549884b3953478c532f0f760eb030f1fb99ad21e 100644
--- a/corsika/framework/core/ParticleProperties.hpp
+++ b/corsika/framework/core/ParticleProperties.hpp
@@ -48,9 +48,9 @@ namespace corsika {
   using PDGCodeType = std::underlying_type<PDGCode>::type;
 
   // forward declarations to be used in GeneratedParticleProperties
-  int16_t constexpr get_charge_number(Code);     //!< electric charge in units of e
-  ElectricChargeType constexpr get_charge(Code); //!< electric charge
-  HEPMassType constexpr get_mass(Code);          //!< mass
+  int16_t constexpr get_charge_number(Code const);     //!< electric charge in units of e
+  ElectricChargeType constexpr get_charge(Code const); //!< electric charge
+  HEPMassType constexpr get_mass(Code const);          //!< mass
   HEPEnergyType constexpr get_energy_threshold(
       Code const); //!< get energy threshold below which the particle is discarded, by
                    //!< default set to particle mass
@@ -67,24 +67,24 @@ namespace corsika {
   }
 
   //! Particle code according to PDG, "Monte Carlo Particle Numbering Scheme"
-  PDGCode constexpr get_PDG(Code);
-  std::string_view constexpr get_name(Code); //!< name of the particle as string
-  TimeType constexpr get_lifetime(Code);     //!< lifetime
+  PDGCode constexpr get_PDG(Code const);
+  std::string_view constexpr get_name(Code const); //!< name of the particle as string
+  TimeType constexpr get_lifetime(Code const);     //!< lifetime
 
   //! true iff the particle is a hard-coded nucleus or Code::Nucleus
-  bool constexpr is_nucleus(Code);
-  bool constexpr is_hadron(Code);    //!< true iff particle is hadron
-  bool constexpr is_em(Code);        //!< true iff particle is electron, positron or gamma
-  bool constexpr is_muon(Code);      //!< true iff particle is mu+ or mu-
-  bool constexpr is_neutrino(Code);  //!< true iff particle is (anti-) neutrino
-  int constexpr get_nucleus_A(Code); //!< returns A for hard-coded nucleus, otherwise 0
-  int constexpr get_nucleus_Z(Code); //!< returns Z for hard-coded nucleus, otherwise 0
+  bool constexpr is_nucleus(Code const);
+  bool constexpr is_hadron(Code const);    //!< true iff particle is hadron
+  bool constexpr is_em(Code const);        //!< true iff particle is electron, positron or gamma
+  bool constexpr is_muon(Code const);      //!< true iff particle is mu+ or mu-
+  bool constexpr is_neutrino(Code const);  //!< true iff particle is (anti-) neutrino
+  int constexpr get_nucleus_A(Code const); //!< returns A for hard-coded nucleus, otherwise 0
+  int constexpr get_nucleus_Z(Code const); //!< returns Z for hard-coded nucleus, otherwise 0
 
   //! returns mass of (A,Z) nucleus, disregarding binding energy
   HEPMassType get_nucleus_mass(unsigned int const, unsigned int const);
 
   //! convert PDG code to CORSIKA 8 internal code
-  Code convert_from_PDG(PDGCode);
+  Code convert_from_PDG(PDGCode const);
 
   std::initializer_list<Code> constexpr get_all_particles();