For a debt instrument to be considered a safe asset, its liquidity must be preserved – it can be bought and sold without a loss – especially when interest rates fluctuate significantly. This article measures the liquidity of French sovereign debt by analysing the “free float” – the debt that can be traded on financial markets. It finds that the liquidity of sovereign securities with a lower free float declined more during the Covid crisis. The Eurosystem’s securities lending facility has helped to mitigate the scarcity effect created by the decline in free float since 2015. Moreover, during the period of liquidity stress that started to subside at the end of March 2020, liquidity deteriorated first in the repo market, then in the cash market and finally in the futures market. Nevertheless, in a global context where liquidity stress episodes are more frequent, French public debt remains one of the most liquid in Europe.