diff --git a/tests/fortify_test.cpp b/tests/fortify_test.cpp
index 7b64fbf..64194c8 100644
--- a/tests/fortify_test.cpp
+++ b/tests/fortify_test.cpp
@@ -958,7 +958,8 @@
 
 TEST(TEST_NAME, memcpy_chk_max_int_size) {
   char buf[10];
-  void* res = __memcpy_chk(buf, "012345678", sizeof(buf), (size_t)-1);
+  size_t buf_size = atoi("-1");
+  void* res = __memcpy_chk(buf, "012345678", sizeof(buf), buf_size);
   ASSERT_EQ((void*)buf, res);
   ASSERT_EQ('0',  buf[0]);
   ASSERT_EQ('1',  buf[1]);