diff --git a/rostests/apitests/crt/_vsnwprintf.c b/rostests/apitests/crt/_vsnwprintf.c
index 3f2bad91ca8..4fc9f283fb8 100644
--- a/rostests/apitests/crt/_vsnwprintf.c
+++ b/rostests/apitests/crt/_vsnwprintf.c
@@ -19,7 +19,7 @@ static void call_varargs(wchar_t* buf, size_t buf_size, int expected_ret, LPCWST
     int ret;
     /* Test the basic functionality */
     va_start(args, formatString);
-    ret = _vsnwprintf(buf, 255, formatString, args);
+    ret = _vsnwprintf(buf, buf_size, formatString, args);
     ok(expected_ret == ret, "Test failed: expected %i, got %i.\n", expected_ret, ret);
 }