The incommensurate structure of gamma-bis(n-propyl-ammonium) tetrachloromanganate(II) (gamma-PAMC) at 365 K has been determined in the superspace group Abma(alpha01)000. Main reflections and satellites up to second order have been included. Besides the harmonic model, anharmonic displacive and Debye-Waller factor modulations have been investigated. Anharmonicities of the displacive modulation functions are negligible. Global phason-correction terms significantly improve the agreement of the second-order satellites. Within the resolution of the experiment, the atomic amplitudon/phason correction converges to the expected theoretical values for the Mn and Cl atoms. The final agreement factors for a phason-corrected displacive harmonic modulation are R(all) = 0.052 (1056 reflections) [R(main) = 0.046 (369 reflections), R(1st order) = 0.057 (627 reflections), R(2nd order) = 0.137 (60 reflections)]. [References: 29]