diff --git a/k4MarlinWrapper/k4MarlinWrapper/MarlinProcessorWrapper.h b/k4MarlinWrapper/k4MarlinWrapper/MarlinProcessorWrapper.h
index e0d206e6..1c09b17c 100644
--- a/k4MarlinWrapper/k4MarlinWrapper/MarlinProcessorWrapper.h
+++ b/k4MarlinWrapper/k4MarlinWrapper/MarlinProcessorWrapper.h
@@ -66,7 +66,7 @@ class MarlinProcessorWrapper : public Gaudi::Algorithm {
 
 private:
   std::string        m_verbosity = "ERROR";
-  marlin::Processor* m_processor = nullptr;
+  mutable marlin::Processor* m_processor = nullptr;
 
   /// Load libraries specified by MARLIN_DLL environment variable
   StatusCode loadProcessorLibraries() const;