diff --git a/utils/include/edm4hep/utils/ParticleIDUtils.h b/utils/include/edm4hep/utils/ParticleIDUtils.h
index 738b3c4f..d9c2791f 100644
--- a/utils/include/edm4hep/utils/ParticleIDUtils.h
+++ b/utils/include/edm4hep/utils/ParticleIDUtils.h
@@ -55,6 +55,7 @@ class PIDHandler {
 public:
   PIDHandler() = default;
   ~PIDHandler() = default;
+  // Copies are not allowed to avoid copying the internal maps
   PIDHandler(const PIDHandler&) = delete;
   PIDHandler& operator=(const PIDHandler&) = delete;
   PIDHandler(PIDHandler&&) = default;