diff --git a/utils.hpp b/utils.hpp
index fc8144c..1a695f4 100644
--- a/utils.hpp
+++ b/utils.hpp
@@ -56,7 +56,8 @@
  * @param[out] dstFile - destination file
  * @return
  **/
-void mergeFiles(std::vector<std::string>& srcFiles, std::string& dstFile);
+void mergeFiles(const std::vector<std::string>& srcFiles,
+                const std::string& dstFile);
 
 namespace internal
 {