The enthalpy calibration coefficient of a heat flux DSC instrument is temperature-dependent and therefore does not maintain a constant value across the entire temperature range of the measured DSC peak. Standard calibration procedures do not take into account any changes in this calibration coefficient during the melting peak of calibration materials. This produces a systematic error in enthalpy calibration, and in the further enthalpy evaluations of unknown materials. This systematic error is high for wide calibration peaks, measured with high heating rates and ceramic crucibles, and can be detected by heat flux DSC instruments. The current work estimates the value of this error and proposes an improvement to the enthalpy calibration procedure by using a DSC weighted mean temperature. (C) 2011 Elsevier B.V. All rights reserved.