R Bootstrap Error - 'Original' Not Found

Question

I am trying to bootstrap the standard errors of the parameter estimates in a glm, and I'm having a little trouble with the bootstrap step. I have defined my function as follows...

boot.fn=function(data,index){
          return(eval(substitute(coef(glm(glm.formula,
                      family = tweedie(var.power=1.5,link.power=0),
                      data=data,
                      subset=index,
                      weights=EXPOSURE_COLL
                      )))))  
}

...and this function runs without error on its own. However, when I run the bootstrap...

set.seed(1977)
boot(coll.train,boot.fn,1000)

...I get the following error message:

Error in eval(expr, envir, enclos) : object 'original' not found 

Any help anyone can provide is greatly appreciated!