Saying Aameen in one's heart in Salaah

As far as I am aware, speaking intentionally or unintentionally will nullify the salaah and it will have to be re-prayed again according to the hanafi maddhab (although, if I am incorrect in my understanding then please correct me jazak Allah khayr). The question I would like to ask is that say for example, if I recite اَللَّهُمَّ رَبَّنَا آتِنَا فِي الدُّنْيَا حَسَنَةً وَفِي الْآخِرَةِ حَسَنَةً وَقِنَا عَذَابَ النَّارِ and in my heart I say Aameen but my tongue may move slightly unintentionally, however there is no sound of any letters coming out, can that be classed as speaking in Salaah?