diff --git a/Processes/Sibyll/Interaction.cc b/Processes/Sibyll/Interaction.cc
index 06d301e3a9f4d264e3b6b56c969fd8d3742269cc..b16d48332a76aaa84edd403ed1a3736487a0269e 100644
--- a/Processes/Sibyll/Interaction.cc
+++ b/Processes/Sibyll/Interaction.cc
@@ -171,7 +171,7 @@ namespace corsika::process::sibyll {
       int i = -1;
       si::CrossSectionType weightedProdCrossSection = 0_mbarn;
       // get weights of components from environment/medium
-      const auto w = mediumComposition.GetFractions();
+      const auto& w = mediumComposition.GetFractions();
       // loop over components in medium
       for (auto const targetId : mediumComposition.GetComponents()) {
         i++;