To measure ammonia gas, organic sensors constitute a promising technology due to their low cost of production and their ability to work at room temperature. However, the effect of interfering species such as humidity may be detrimental to the measurement reliability of the sensor. In comparison to traditional solvents used to disperse the conductive polymer in solution, doped polyaniline is dispersed in toluene here. The change of solvent leads to an interesting active layer microstructure, composed of microscopic needles, whose sensing performances are little impacted by humidity. The sensitivity of this new material, its limit of detection as well as its stability over 6 months are really promising compared to sensors made in dichloroacetic acid.