diff --git a/src/algorithms/digi/PhotoMultiplierHitDigi.cc b/src/algorithms/digi/PhotoMultiplierHitDigi.cc
index 6704a14e18..e74b80202d 100644
--- a/src/algorithms/digi/PhotoMultiplierHitDigi.cc
+++ b/src/algorithms/digi/PhotoMultiplierHitDigi.cc
@@ -17,6 +17,7 @@
 
 #include <Evaluator/DD4hepUnits.h>
 #include <algorithms/logger.h>
+#include <edm4eic/EDM4eicVersion.h>
 #include <edm4hep/Vector3d.h>
 #include <fmt/core.h>
 #include <math.h>
@@ -168,11 +169,16 @@ void PhotoMultiplierHitDigi::process(
 
                 // build `MCRecoTrackerHitAssociation` (for non-noise hits only)
                 if(!data.sim_hit_indices.empty()) {
-                  auto hit_assoc = hit_assocs->create();
-                  hit_assoc.setWeight(1.0); // not used
-                  hit_assoc.setRawHit(raw_hit);
-                  for(auto i : data.sim_hit_indices)
+                  for(auto i : data.sim_hit_indices) {
+                    auto hit_assoc = hit_assocs->create();
+                    hit_assoc.setWeight(1.0 / data.sim_hit_indices.size()); // not used
+                    hit_assoc.setRawHit(raw_hit);
+#if EDM4EIC_VERSION_MAJOR >= 6
+                    hit_assoc.setSimHit(sim_hits->at(i));
+#else
                     hit_assoc.addToSimHits(sim_hits->at(i));
+#endif
+                  }
                 }
             }
         }
diff --git a/src/algorithms/digi/SiliconTrackerDigi.cc b/src/algorithms/digi/SiliconTrackerDigi.cc
index 79197b5816..5833f5ae17 100644
--- a/src/algorithms/digi/SiliconTrackerDigi.cc
+++ b/src/algorithms/digi/SiliconTrackerDigi.cc
@@ -4,6 +4,7 @@
 #include "SiliconTrackerDigi.h"
 
 #include <Evaluator/DD4hepUnits.h>
+#include <edm4eic/EDM4eicVersion.h>
 #include <edm4hep/MCParticleCollection.h>
 #include <edm4hep/Vector3d.h>
 #include <edm4hep/Vector3f.h>
@@ -97,7 +98,11 @@ void SiliconTrackerDigi::process(
             auto hitassoc = associations->create();
             hitassoc.setWeight(1.0);
             hitassoc.setRawHit(item.second);
+#if EDM4EIC_VERSION_MAJOR >= 6
+            hitassoc.setSimHit(sim_hit);
+#else
             hitassoc.addToSimHits(sim_hit);
+#endif
           }
         }
 
diff --git a/src/algorithms/pid/IrtCherenkovParticleID.cc b/src/algorithms/pid/IrtCherenkovParticleID.cc
index 4b2cd508d6..13de55e18d 100644
--- a/src/algorithms/pid/IrtCherenkovParticleID.cc
+++ b/src/algorithms/pid/IrtCherenkovParticleID.cc
@@ -11,6 +11,7 @@
 #include <TString.h>
 #include <TVector3.h>
 #include <edm4eic/CherenkovParticleIDHypothesis.h>
+#include <edm4eic/EDM4eicVersion.h>
 #include <edm4eic/TrackPoint.h>
 #include <edm4hep/MCParticleCollection.h>
 #include <edm4hep/SimTrackerHitCollection.h>
@@ -218,17 +219,22 @@ std::map<std::string, std::unique_ptr<edm4eic::CherenkovParticleIDCollection>> e
           for(const auto& hit_assoc : *in_hit_assocs) {
             if(hit_assoc.getRawHit().isAvailable()) {
               if(hit_assoc.getRawHit().id() == raw_hit.id()) {
+#if EDM4EIC_VERSION_MAJOR >= 6
+                mc_photon = hit_assoc.getSimHit().getMCParticle();
+#else
                 // hit association found, get the MC photon and break the loop
-                // FIXME: occasionally there will be more than one photon associated with a hit;
-                // for now let's just take the first one...
                 if(hit_assoc.simHits_size() > 0) {
                   mc_photon = hit_assoc.getSimHits(0).getMCParticle();
+#endif
                   mc_photon_found = true;
                   if(mc_photon.getPDG() != -22)
                     m_log->warn("non-opticalphoton hit: PDG = {}",mc_photon.getPDG());
+#if EDM4EIC_VERSION_MAJOR >= 6
+#else
                 }
                 else if(m_cfg.CheatModeEnabled())
                   m_log->error("cheat mode enabled, but no MC photons provided");
+#endif
                 break;
               }
             }