diff --git a/Processes/StackInspector/StackInspector.cc b/Processes/StackInspector/StackInspector.cc
index 814763d5cbfcbc0bd4201db70f220dc4e8ea123f..e56503378ed5abfc15578c474ed0afd4d54d6412 100644
--- a/Processes/StackInspector/StackInspector.cc
+++ b/Processes/StackInspector/StackInspector.cc
@@ -37,7 +37,7 @@ template <typename TStack>
 StackInspector<TStack>::~StackInspector() {}
 
 template <typename TStack>
-process::EProcessReturn StackInspector<TStack>::DoStack(TStack& vS) {
+process::EProcessReturn StackInspector<TStack>::DoStack(TStack const& vS) {
   if (!fReport) return process::EProcessReturn::eOk;
   [[maybe_unused]] int i = 0;
   HEPEnergyType Etot = 0_GeV;
diff --git a/Processes/StackInspector/StackInspector.h b/Processes/StackInspector/StackInspector.h
index 57a929dd2362b302d43d05175878a257c5c8a832..62f36eeebae774f74d26953697707e698c75da6e 100644
--- a/Processes/StackInspector/StackInspector.h
+++ b/Processes/StackInspector/StackInspector.h
@@ -30,7 +30,7 @@ namespace corsika::process {
       ~StackInspector();
 
       void Init();
-      EProcessReturn DoStack(TStack&);
+      EProcessReturn DoStack(TStack const&);
 
     private:
       bool fReport;