This is why I call my references and remind them of what I want them to say.
"Hi X, as we discussed I used you for a reference for a Quality Assurance Developer role from our time together at FooCorp. I mentioned our debugging of the priority inversion problem in our server, writing the kernel module, and working with you to integrate scripting. Thanks!"
"Hi X, as we discussed I used you for a reference for a Quality Assurance Developer role from our time together at FooCorp. I mentioned our debugging of the priority inversion problem in our server, writing the kernel module, and working with you to integrate scripting. Thanks!"