diff --git a/Framework/ProcessSequence/InteractionProcess.h b/Framework/ProcessSequence/InteractionProcess.h
index 96472755376c4cf630f8ac92e92c5c08eb1c2f48..723cbf02fcc7ce443d968300293ccc44d1b40811 100644
--- a/Framework/ProcessSequence/InteractionProcess.h
+++ b/Framework/ProcessSequence/InteractionProcess.h
@@ -36,7 +36,7 @@ namespace corsika::process {
     /// here starts the interface-definition part
     // -> enforce derived to implement DoInteraction...
     template <typename P, typename S>
-    inline EProcessReturn DoInteraction(P&, S&);
+    EProcessReturn DoInteraction(P&, S&);
 
     template <typename Particle, typename Track>
     corsika::units::si::GrammageType GetInteractionLength(Particle& p, Track& t);