The invention relates to a reservoir assembly for a pagewidth printhead cartridge. The cartridge has a fluid distribution molding with priming inlets in fluid communication with fluid channels for supplying printing fluid to a plurality of printhead integrated circuits. The reservoir assembly includes a reservoir compartment arranged in fluid communication with the fluid channels via a fluid outlet. The reservoir includes a porous absorbent material located inside the compartment to absorb printing fluid delivered via the priming inlets. The reservoir assembly also includes a bypass fluid path arranging the fluid outlet and a well region of the compartment in fluid communication, said bypass fluid path having a bypass valve to facilitate priming the reservoir compartment with printing fluid.