This paper uses an instrumental variable approach to study whether public debt has a causal effect on economic growth in a sample of OECD countries. The results are consistent with the existing literature that has found a negative correlation between debt and growth. However, the link between debt and growth disappears once we instrument debt with a variable that captures valuation effects brought about by the interaction between foreign currency debt and exchange rate volatility. We conduct a battery of robustness tests and show that our results are not affected by weak instrument problems and are robust to relaxing our exclusion restriction.