@sova thanks for the answer, but i only used the grammar above as an example (taken from https://github.com/Engelberg/instaparse/blob/master/docs/ExperimentalFeatures.md#auto-whitespace). My problem is that i need the tokens of the grammar to be whitespace separated, so that keywords of the grammar cannot be "merged" with the following tokens. For example: replace word in the grammar i pasted with some keyword like 'power' , which then should be followed by some number. Then i need the string 'power 100' to be valid, but not the string power100. The problem is that the :auto-whitespace :standard feature allows both.