The Lithium-PEG method to transform yeast cells is a common experiment used by most yeast laboratories. After several optimizations, this method can yield up to 10 6 transformants / µg of plasmid. Some experiments such as library screening or complex transformation require to maximize transformation yield. Here we show that the addition of a 2M sorbitol solution acts as an osmo-protectant during and after heat shock and increases ten-fold the transformation rate. This optimization requires only one additional pipetting step compared to the initial protocol, and is therefore practical for a daily use.