diff --git a/include/kabufuda/Util.hpp b/include/kabufuda/Util.hpp
index 406e0f5..5af53f2 100644
--- a/include/kabufuda/Util.hpp
+++ b/include/kabufuda/Util.hpp
@@ -208,8 +208,8 @@ public:
     std::wstring operator+(const std::wstring_view other) const { return m_sys + other.data(); }
 };
 inline std::wstring operator+(const std::wstring_view lhs, const SystemStringConv& rhs) { return std::wstring(lhs) + rhs.c_str(); }
-#ifndef _S
-#define _S(val) L##val
+#ifndef _SYS_STR
+#define _SYS_STR(val) L##val
 #endif
 typedef struct _stat Sstat;
 #else
diff --git a/test/main.cpp b/test/main.cpp
index 4cea0c8..cafa73f 100644
--- a/test/main.cpp
+++ b/test/main.cpp
@@ -4,7 +4,7 @@
 int main()
 {
     kabufuda::Card mc{"GM8E", "01"};
-    mc.open(_S("test.USA.raw"));
+    mc.open(_SYS_STR("test.USA.raw"));
     mc.format(kabufuda::ECardSlot::SlotA, kabufuda::ECardSize::Card2043Mb);
     uint64_t a = 0;
     mc.getSerial(a);