In this paper, a modified constitutive relation to model the dynamic strain aging phenomenon is proposed based on the previous model of Voyiadjis-Abed. The dynamic strain aging phenomenon is typically observed in metals for a certain range of strain rates and temperatures. In quasi-static loading experiments which were performed by Abed et al. (2017) using a C45 steel for a large range of temperatures from 298 K to 923 K, a stress increase due to the dynamics strain aging was observed according to the temperature variation. Using both a phenomenological Johnson-Cook model and a physically based Voyiadjis-Abed model, this stress increase cannot be captured when dynamic strain aging is active. The Voyiadjis-Abed model is modified in the present work by means of a mathematical expression of the Weibull distribution that is derived based on a physically based mechanism of evolution of the dislocation density.