The rate constant of NNH + O --> NH + NO has been derived by comparing experiments in low-pressure (0.05 and 0.103 bar) hydrogen-air flames at similar to 1200 K [1] with modeling that uses an updated detailed H/N/O kinetic scheme. To match calculations with experimental [NO] profiles along these names, the currently adopted rate constant of this reaction has to be reduced significantly (by similar to 50%). Combination of the adjusted rate constant with measurements in the range 1800 to 2500 K strongly suggests a non-zero activation energy for the reaction. The rate constant derived from 1100 to 2500 K is k(1) = (2 +/-1) x 10(14) exp (-16.8 +/-4.2 kJ/mol.RT) cm(3)/\mol/s. The sum of the rate constants of every channel of the reaction Nn + NO --> Products, including that of the reverse Reaction -1 proposed in the present work, is in good agreement with available experimental data.