diff --git a/src/openms/include/OpenMS/FORMAT/HANDLERS/XMLHandler.h b/src/openms/include/OpenMS/FORMAT/HANDLERS/XMLHandler.h
index 0ae4a1fadac..c43a63a54d8 100644
--- a/src/openms/include/OpenMS/FORMAT/HANDLERS/XMLHandler.h
+++ b/src/openms/include/OpenMS/FORMAT/HANDLERS/XMLHandler.h
@@ -390,9 +390,6 @@ namespace OpenMS
       /// Writes the contents to a stream.
       virtual void writeTo(std::ostream & /*os*/);
 
-      /// Returns the last error description
-      String errorString();
-
       /// handler which support partial loading, implement this method
       virtual LOADDETAIL getLoadDetail() const;
 
@@ -469,9 +466,6 @@ namespace OpenMS
       void checkUniqueIdentifiers_(const std::vector<ProteinIdentification>& prot_ids) const;
 
 protected:
-      /// Error message of the last error
-      mutable String error_message_;
-
       /// File name
       String file_;
 
diff --git a/src/openms/source/FORMAT/HANDLERS/MzMLHandlerHelper.cpp b/src/openms/source/FORMAT/HANDLERS/MzMLHandlerHelper.cpp
index 402fd6bc299..d5a109e5136 100644
--- a/src/openms/source/FORMAT/HANDLERS/MzMLHandlerHelper.cpp
+++ b/src/openms/source/FORMAT/HANDLERS/MzMLHandlerHelper.cpp
@@ -43,20 +43,20 @@ namespace OpenMS::Internal
 
     void MzMLHandlerHelper::warning(int mode, const String & msg, UInt line, UInt column)
     {
-      String error_message_;
+      String error_message;
       if (mode == 0)
       {
-        error_message_ =  String("While loading '") + "': " + msg;
+        error_message =  String("While loading '") + "': " + msg;
       }
       else if (mode == 1)
       {
-        error_message_ =  String("While storing '") + "': " + msg;
+        error_message =  String("While storing '") + "': " + msg;
       }
       if (line != 0 || column != 0)
       {
-        error_message_ += String("( in line ") + line + " column " + column + ")";
+        error_message += String("( in line ") + line + " column " + column + ")";
       }
-      OPENMS_LOG_WARN << error_message_ << std::endl;
+      OPENMS_LOG_WARN << error_message << std::endl;
     }
 
   String MzMLHandlerHelper::getCompressionTerm_(const PeakFileOptions& opt, MSNumpressCoder::NumpressConfig np, const String& indent, bool use_numpress)
diff --git a/src/openms/source/FORMAT/HANDLERS/XMLHandler.cpp b/src/openms/source/FORMAT/HANDLERS/XMLHandler.cpp
index 32395a4ca18..de597ed6c97 100644
--- a/src/openms/source/FORMAT/HANDLERS/XMLHandler.cpp
+++ b/src/openms/source/FORMAT/HANDLERS/XMLHandler.cpp
@@ -104,70 +104,73 @@ namespace OpenMS::Internal
 
     void XMLHandler::fatalError(ActionMode mode, const String & msg, UInt line, UInt column) const
     {
+      String error_message;
       if (mode == LOAD)
       {
-        error_message_ =  String("While loading '") + file_ + "': " + msg;
+        error_message =  String("While loading '") + file_ + "': " + msg;
 	      // test if file has the wrong extension and is therefore passed to the wrong parser
         // only makes sense if we are loading/parsing a file
 	      FileTypes::Type ft_name = FileHandler::getTypeByFileName(file_);
         FileTypes::Type ft_content = FileHandler::getTypeByContent(file_);
         if (ft_name != ft_content)
         {
-          error_message_ += String("\nProbable cause: The file suffix (") + FileTypes::typeToName(ft_name)
+          error_message += String("\nProbable cause: The file suffix (") + FileTypes::typeToName(ft_name)
                           + ") does not match the file content (" + FileTypes::typeToName(ft_content) + "). "
                           + "Rename the file to fix this.";
         }
       }
       else if (mode == STORE)
       {
-        error_message_ =  String("While storing '") + file_ + "': " + msg;
+        error_message =  String("While storing '") + file_ + "': " + msg;
       }
       if (line != 0 || column != 0)
       {
-        error_message_ += String("( in line ") + line + " column " + column + ")";
+        error_message += String("( in line ") + line + " column " + column + ")";
       }
 
-      OPENMS_LOG_FATAL_ERROR << error_message_ << std::endl;
-      throw Exception::ParseError(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION, file_, error_message_);
+      OPENMS_LOG_FATAL_ERROR << error_message << std::endl;
+      throw Exception::ParseError(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION, file_, error_message);
     }
 
     void XMLHandler::error(ActionMode mode, const String & msg, UInt line, UInt column) const
     {
+      String error_message;
       if (mode == LOAD)
       {
-        error_message_ =  String("Non-fatal error while loading '") + file_ + "': " + msg;
+        error_message =  String("Non-fatal error while loading '") + file_ + "': " + msg;
       }
       else if (mode == STORE)
       {
-        error_message_ =  String("Non-fatal error while storing '") + file_ + "': " + msg;
+        error_message =  String("Non-fatal error while storing '") + file_ + "': " + msg;
       }
       if (line != 0 || column != 0)
       {
-        error_message_ += String("( in line ") + line + " column " + column + ")";
+        error_message += String("( in line ") + line + " column " + column + ")";
       }
-      OPENMS_LOG_ERROR << error_message_ << std::endl;
+      OPENMS_LOG_ERROR << error_message << std::endl;
     }
 
     void XMLHandler::warning(ActionMode mode, const String & msg, UInt line, UInt column) const
     {
+      String error_message;
       if (mode == LOAD)
       {
-        error_message_ =  String("While loading '") + file_ + "': " + msg;
+        error_message =  String("While loading '") + file_ + "': " + msg;
       }
       else if (mode == STORE)
       {
-        error_message_ =  String("While storing '") + file_ + "': " + msg;
+        error_message =  String("While storing '") + file_ + "': " + msg;
       }
       if (line != 0 || column != 0)
       {
-        error_message_ += String("( in line ") + line + " column " + column + ")";
+        error_message += String("( in line ") + line + " column " + column + ")";
       }
 
 // warn only in Debug mode but suppress warnings in release mode (more happy users)
 #ifdef OPENMS_ASSERTIONS
-      OPENMS_LOG_WARN << error_message_ << std::endl;
+      OPENMS_LOG_WARN << error_message << std::endl;
 #else
-      OPENMS_LOG_DEBUG << error_message_ << std::endl;
+      OPENMS_LOG_DEBUG << error_message << std::endl;
 #endif
 
     }
@@ -188,11 +191,6 @@ namespace OpenMS::Internal
     {
     }
 
-    String XMLHandler::errorString()
-    {
-      return error_message_;
-    }
-
     SignedSize XMLHandler::cvStringToEnum_(const Size section, const String & term, const char * message, const SignedSize result_on_error)
     {
       OPENMS_PRECONDITION(section < cv_terms_.size(), "cvStringToEnum_: Index overflow (section number too large)");