diff --git a/k4FWCore/components/Writer.cpp b/k4FWCore/components/Writer.cpp
index a613be8e..b0a2538c 100644
--- a/k4FWCore/components/Writer.cpp
+++ b/k4FWCore/components/Writer.cpp
@@ -117,7 +117,7 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
     }
 
     config_metadata_frame.putParameter("gaudiConfigOptions", config_data);
-    if (auto env_key4hep_stack = std::getenv("KEY4HEP_STACK")) {
+    if (const char* env_key4hep_stack = std::getenv("KEY4HEP_STACK")) {
       config_metadata_frame.putParameter("key4hepstack", env_key4hep_stack);
     }
     iosvc->getWriter()->writeFrame(config_metadata_frame, "configuration_metadata");