In Fig. 5 on p. 311 of our Phys. Lett. B 740 (2015) 303 an adjustment by 180∘ is required for the phases with respect to the L=2,M=1 wave, of the following waves: L=1,3,5 with M=1, and L=2 with M=2. After this correction (Fig. 5 (corrected) below), the extracted partial waves describe the angular distribution of the η(′) in the Gottfried-Jackson (GJ) frame, using Eq. (4) with implicit Condon-Shortley phase convention. The other results of our paper are not affected. The right-handed GJ coordinate system was defined by the z-axis pointing in the direction of the beam in the η(′)π− center-of-mass system and the y-axis pointing in the direction of precoilGJ×pbeamGJ.