A start quantity adaptation value (ST_AD) is adapted as a function of a variable that is characteristic of a rotational speed profile during the start (ST) of the internal combustion engine. A lambda adaptation value (LAM_AD) is adapted as a function of at least one control parameter (LAM_RP) of the lambda controller if a preset condition (COND) is met, which presupposes the existence of a quasi-stationary operating state. An intermediate correction value (ZW_KOR) is adapted as a function of a change of the start quantity adaptation value (ST_AD) since a last adaptation of the lambda adaptation value (LAM_AD). A fuel mass (MFF) to be metered is determined as a function of at least one operating variable (BG) of the internal combustion engine. The fuel mass (MFF) to be metered is corrected during the start (ST) of the internal combustion engine by means of the start quantity adaptation value (ST_AD). The fuel mass (MFF) to be metered outside of the start (ST) of the internal combustion engine is corrected as a function of the lambda adaptation value (LAM_AD). The fuel mass (MFF) to be metered is corrected as a function of the intermediate correction value (ZW_KOR) until for the first time after the respective start (ST) the lambda adaptation value (LAM_AD) is adapted.