The present invention is directed to a new composition for performing a nucleic acid amplification reaction comprising (i) a thermostable DNA-Polymerase, (ii) a thermostable 3'-5' Exonuclease, and (iii) at least one primer for nucleic acid amplification with a modified 3' terminal residue which is not elongated by said thermostable DNA-Polymerase as well as methods for performing a PCR reaction using this composition. Furthermore, the method is directed to kits comprising such a composition.