Aggregate US bank lending to firms tends to expand following adverse macroeconomic shocks, such as the outbreak of COVID-19 or a monetary policy tightening. Based on detailed loan-level supervisory data, this column shows that these responses are almost entirely explained by large firms drawing on their bank credit lines. However, funding stability for large firms may imply that smaller firms face tighter borrowing conditions. The authors show that such a crowding out effect was at play during the COVID-19 crisis and explore the implications of such spillovers within a structural model.