We report on the diffraction peak shape evolution from cementite particles in three steel microstructures, recorded during in-situ tensile deformation at room temperature. We demonstrate that in a bainitic tempered steel the observed peak broadening and asymmetry of cementite is a purely elastic effect, related to the heterogeneity of the microstructure. This result warns against the indiscriminate use of peak profile analysis to derive information on plastic deformation in cementite. (C) 2014 Elsevier Ltd. All rights reserved.