diff --git a/test/nm_frame.cpp b/test/nm_frame.cpp
index 5a18579..41cff42 100644
--- a/test/nm_frame.cpp
+++ b/test/nm_frame.cpp
@@ -31,7 +31,8 @@
 
 int main()
 {
-	CYBOZU_TEST_EQUAL(sizeof(Xbyak::Operand), 4u);
+	// the size of Operand exceeds 32 bit.
+	CYBOZU_TEST_EQUAL(sizeof(Xbyak::Operand), 8u);
 	Sample s;
 	s.gen();
 	ErrorSample es;