diff --git a/Processes/Sibyll/Interaction.h b/Processes/Sibyll/Interaction.h
index 2a4c02d063242ae247f2a3e473f9c179ca5a81cb..b403d09cfa79f5cdcc58cca8ff68ed54d1b65b23 100644
--- a/Processes/Sibyll/Interaction.h
+++ b/Processes/Sibyll/Interaction.h
@@ -185,9 +185,10 @@ namespace corsika::process::sibyll {
       cout << "ProcessSibyll: "
            << "DoInteraction: " << corsikaBeamId << " interaction? "
            << process::sibyll::CanInteract(corsikaBeamId) << endl;
+      
       if(corsika::particles::IsNucleus(corsikaBeamId)){
-	// nuclei handled by different process, skip
-	return process::EProcessReturn::eOk;
+	// nuclei handled by different process, this should not happen
+	throw std::runtime_error("Nuclear projectile are not handled by SIBYLL!");
       }
       
       if (process::sibyll::CanInteract(corsikaBeamId)) {
diff --git a/Processes/Sibyll/NuclearInteraction.h b/Processes/Sibyll/NuclearInteraction.h
index d7f926fd8fdfaf23a81efbdbe0b6d51ca988c9ed..63ee3aa136e37d532ea40d06318c6f0e68e00217 100644
--- a/Processes/Sibyll/NuclearInteraction.h
+++ b/Processes/Sibyll/NuclearInteraction.h
@@ -203,7 +203,6 @@ namespace corsika::process::sibyll {
       if(!IsNucleus(corsikaProjId)){
 	// this should not happen
 	throw std::runtime_error("Non nuclear projectile in NUCLIB!");
-	return process::EProcessReturn::eOk;
       }
 
       fCount++;