聚合物核心-阿贾克斯在新的聚合物元素中表现出奇怪的行为

I put a core-ajax element in a new polymer element but instead of a response I get an Access Control error. When I use the element alone in my index.html on the same url, I get a regular response. Any idea why this is happening?I put a core-ajax element in a new polymer elem