diff --git a/src/util/regex/regex-top-matcher.hpp b/src/util/regex/regex-top-matcher.hpp
index fc4a0df..4d9c01e 100644
--- a/src/util/regex/regex-top-matcher.hpp
+++ b/src/util/regex/regex-top-matcher.hpp
@@ -43,7 +43,7 @@
 
 private:
   std::string
-  getItemFromExpand(const std::string& expand, int & offset);
+  getItemFromExpand(const std::string& expand, size_t& offset);
 
   static std::string
   convertSpecialChar(const std::string& str);