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The impact of thermal expansion and the corresponding non-Boussinesq effects on porous media convection are considered. The results show that the non-Boussinesq effects decouple from the rest, and solving the Boussinesq system separately is needed even when non-Boussinesq effects are being investigated. The thermal expansion is shown to have a lasting impact on the post-transient convection only for values of Rayleigh number substantially beyond the convection threshold, where the amplitude of convection is not small. In the neighbourhood of the convection threshold the thermal expansion has only a transient impact on the solution. It is also evident from the results that the neglect of the time derivative term in the extended Darcy equation might introduce a significant error when oscillatory effects are present.