diff --git a/Common/Tools/Multiplicity/MultModule.h b/Common/Tools/Multiplicity/MultModule.h
index bed8817c124..f3122106de4 100644
--- a/Common/Tools/Multiplicity/MultModule.h
+++ b/Common/Tools/Multiplicity/MultModule.h
@@ -440,6 +440,7 @@ class MultModule
     internalOpts.mEnabledTables.resize(nTablesConst, 0);
 
     LOGF(info, "Configuring tables to generate");
+    LOGF(info, "Metadata information: isMC? %i", metadataInfo.isMC());
     const auto& workflows = context.services().template get<o2::framework::RunningWorkflowInfo const>();
 
     TString listOfRequestors[nTablesConst];
@@ -505,16 +506,6 @@ class MultModule
       listOfRequestors[kPVMults].Append(Form("%s ", "dependency check"));
     }
 
-    // capture the need for PYTHIA calibration in Pb-Pb runs
-    if (metadataInfo.isMC() && mRunNumber >= 544013 && mRunNumber <= 545367) {
-      internalOpts.generatorName.value = "PYTHIA";
-    }
-
-    // capture the need for PYTHIA calibration in light ion runs automatically
-    if (metadataInfo.isMC() && mRunNumber >= 564250 && mRunNumber <= 564472) {
-      internalOpts.generatorName.value = "PYTHIA";
-    }
-
     // list enabled tables
     for (int i = 0; i < nTablesConst; i++) {
       // printout to be improved in the future
@@ -1145,6 +1136,20 @@ class MultModule
   {
     if (bc.runNumber() != mRunNumberCentrality) {
       mRunNumberCentrality = bc.runNumber(); // mark that this run has been attempted already regardless of outcome
+      LOGF(info, "centrality loading procedure for timestamp=%llu, run number=%d", bc.timestamp(), bc.runNumber());
+
+      // capture the need for PYTHIA calibration in Pb-Pb runs
+      if (metadataInfo.isMC() && mRunNumber >= 544013 && mRunNumber <= 545367) {
+        LOGF(info, "This is MC for Pb-Pb. Setting generatorName automatically to PYTHIA");
+        internalOpts.generatorName.value = "PYTHIA";
+      }
+
+      // capture the need for PYTHIA calibration in light ion runs automatically
+      if (metadataInfo.isMC() && mRunNumber >= 564250 && mRunNumber <= 564472) {
+        LOGF(info, "This is MC for light ion runs. Setting generatorName automatically to PYTHIA");
+        internalOpts.generatorName.value = "PYTHIA";
+      }
+
       LOGF(info, "centrality loading procedure for timestamp=%llu, run number=%d", bc.timestamp(), bc.runNumber());
       TList* callst = nullptr;
       // Check if the ccdb path is a root file
@@ -1258,6 +1263,10 @@ class MultModule
       auto populateTable = [&](auto& table, struct CalibrationInfo& estimator, float multiplicity, bool isInelGt0) {
         const bool assignOutOfRange = internalOpts.embedINELgtZEROselection && !isInelGt0;
         auto scaleMC = [](float x, const float pars[6]) {
+          float core = ((pars[0] + pars[1] * std::pow(x, pars[2])) - pars[3]) / pars[4];
+          if (core < 0.0f) {
+            return 0.0f; // this should be marked as low multiplicity and not mapped, core^pars[5] would be NaN
+          }
           return std::pow(((pars[0] + pars[1] * std::pow(x, pars[2])) - pars[3]) / pars[4], 1.0f / pars[5]);
         };
 
@@ -1343,6 +1352,10 @@ class MultModule
       ConfigureCentralityRun2(ccdb, metadataInfo, firstbc);
 
       auto scaleMC = [](float x, const float pars[6]) {
+        float core = ((pars[0] + pars[1] * std::pow(x, pars[2])) - pars[3]) / pars[4];
+        if (core < 0.0f) {
+          return 0.0f; // this should be marked as low multiplicity and not mapped, core^pars[5] would be NaN
+        }
         return std::pow(((pars[0] + pars[1] * std::pow(x, pars[2])) - pars[3]) / pars[4], 1.0f / pars[5]);
       };