There are many situations in which a Modelica model needs to handle quantities which are not expressed in the often preferred unscaled SI units. Applying correct unit conversions is extremely important in such situations, and the risk of human error needs to be mitigated using unit-aware technology. Considering the power of unit checking mechanisms in several Modelica tools today, one can be surprised that unit conversion in Modelica still needs to be performed using error-prone user-written formulas and functions. It is demonstrated how automatic and implicit unit conversion can be introduced in Modelica, and that this can be done safely. The benefits of this approach are illustrated in a variety of examples and applications.