literal rule definition overrided by regex

something.peg

// Excluding first block
Let <- "let" // This is overrided by the following, same happens if i put this rule below the Identifier rule
Identifier <- ([a-z_]i+([a-z0-9_]i)*) {
  return string(c.text), nil
}

Of course happens to all keyword like rules

If <- "if" // and so on . . .

I guess, this is part of a much larger peg file, right? It looks like the relevant/important section is missing in this gist. My assumption is, that you have a choice expression some where and that the order in your choice expression is wrong. you have to put the most specific conditions first in your choice expression followed by the more generic ones. See https://godoc.org/github.com/mna/pigeon#hdr-Choice_expression