[en] It was proposed that the narrow P_c(4450) structure observed by the LHCb Collaboration in the reaction Λ_b → J/ψpK might be due to a triangle singularity around the χ_c_1-proton threshold at 4.45 GeV. We discuss the occurrence of a similar triangle singularity in the J/ψp invariant mass distribution for the decay Λ_b → J/ψpπ, which could explain the bump around 4.45 GeV in the data. More precise measurements of this process would provide valuable information towards an understanding of the P_c structures. (orig.)