diff --git a/include/mcl/gmp_util.hpp b/include/mcl/gmp_util.hpp
index d6b6b4d..117ecff 100644
--- a/include/mcl/gmp_util.hpp
+++ b/include/mcl/gmp_util.hpp
@@ -26,6 +26,9 @@
 #if defined(__EMSCRIPTEN__) || defined(__wasm__)
 	#define MCL_USE_VINT
 #endif
+#ifndef MCL_MAX_BIT_SIZE
+	#define MCL_MAX_BIT_SIZE 521
+#endif
 #ifdef MCL_USE_VINT
 #include <mcl/vint.hpp>
 typedef mcl::Vint mpz_class;
diff --git a/include/mcl/op.hpp b/include/mcl/op.hpp
index 36d3703..ded5d1b 100644
--- a/include/mcl/op.hpp
+++ b/include/mcl/op.hpp
@@ -10,9 +10,6 @@
 #include <memory.h>
 #include <mcl/array.hpp>
 
-#ifndef MCL_MAX_BIT_SIZE
-	#define MCL_MAX_BIT_SIZE 521
-#endif
 #if defined(__EMSCRIPTEN__) || defined(__wasm__)
 	#define MCL_DONT_USE_XBYAK
 	#define MCL_DONT_USE_OPENSSL
diff --git a/include/mcl/vint.hpp b/include/mcl/vint.hpp
index 3e2767f..8c1a13f 100644
--- a/include/mcl/vint.hpp
+++ b/include/mcl/vint.hpp
@@ -19,7 +19,7 @@
 	#define MCL_VINT_FIXED_BUFFER
 #endif
 #ifndef MCL_MAX_BIT_SIZE
-	#define MCL_MAX_BIT_SIZE 384
+	#error "define MCL_MAX_BIT_SZIE"
 #endif
 
 #ifndef MCL_SIZEOF_UNIT