diff --git a/file_io/include/aare/file_io/FileInterface.hpp b/file_io/include/aare/file_io/FileInterface.hpp
index 2c61590..2d168b2 100644
--- a/file_io/include/aare/file_io/FileInterface.hpp
+++ b/file_io/include/aare/file_io/FileInterface.hpp
@@ -162,7 +162,7 @@ class FileInterface {
 
     };
 
-  public:
+  protected:
     std::string m_mode;
     std::filesystem::path m_fname;
     std::filesystem::path m_base_path;
diff --git a/file_io/include/aare/file_io/RawFile.hpp b/file_io/include/aare/file_io/RawFile.hpp
index 0ff33bb..65d57f6 100644
--- a/file_io/include/aare/file_io/RawFile.hpp
+++ b/file_io/include/aare/file_io/RawFile.hpp
@@ -112,7 +112,7 @@ class RawFile : public FileInterface {
 
     /**
      * @brief parse the file name to get the extension, base name and index
-    */
+     */
     void parse_fname();
 
     /**
@@ -122,12 +122,12 @@ class RawFile : public FileInterface {
 
     /**
      * @brief parse the metadata of a .raw file
-    */
+     */
     void parse_raw_metadata();
 
     /**
      * @brief parse the metadata of a .json file
-    */
+     */
     void parse_json_metadata();
 
     /**
@@ -144,9 +144,10 @@ class RawFile : public FileInterface {
 
     /**
      * @brief open the subfiles
-    */
+     */
     void open_subfiles();
 
+  private:
     size_t n_subfiles;
     size_t n_subfile_parts;
     std::vector<std::vector<SubFile *>> subfiles;