@saghosh / @Mark Takata (Adobe) https://helpx.adobe.com/coldfusion/cfml-reference/coldfusion-functions/functions-c-d/CallStackGet.html First sentence: "Returns an array of structs". No. It doesn't. It returns an ArrayList. https://trycf.com/gist/2232d3ae3dd1f5be234b10b72329b98d/acf2021?theme=monokai Why does this matter? Some built-in CFML array functions don't work with ArrayLists EG: https://trycf.com/gist/64dc69d09d20e9d2152187ae1d56c2c6/acf2021?theme=monokai (why? Dunno; your problem) So the docs are wrong. But also the function is wrong. ArrayLists are not a thing in CFML. A built-in CFML function should not be returning an ArrayList. It should be returning a coldfusion.runtime.Array.