diff --git a/core-buffer/include/FastH5Writer.hpp b/core-buffer/include/FastH5Writer.hpp
index 60bae46..5658382 100644
--- a/core-buffer/include/FastH5Writer.hpp
+++ b/core-buffer/include/FastH5Writer.hpp
@@ -33,6 +33,10 @@ class FastH5Writer {
     std::unordered_map<std::string, H5::PredType> scalar_metadata_;
 
     void create_file(const std::string& filename);
+    void write_scalar_metadata(
+            const std::string& name,
+            const void* value,
+            const H5::DataType data_type);
 
 public:
     FastH5Writer(
@@ -54,11 +58,6 @@ public:
             const std::string& name,
             const void* value);
 
-    void write_scalar_metadata(
-            const std::string& name,
-            const void* value,
-            const H5::DataType data_type);
-
     void close_file();
 };