diff --git a/benchmarks/backwards_ecal/backwards_ecal.org b/benchmarks/backwards_ecal/backwards_ecal.org
index 38cb99407d275e5af36a3f4a6f5bee4c0cb7e84f..29ab4061d8eeb34a205938c9936a5b27da0a483c 100644
--- a/benchmarks/backwards_ecal/backwards_ecal.org
+++ b/benchmarks/backwards_ecal/backwards_ecal.org
@@ -255,7 +255,7 @@ for clf_label, sigma_rel_FWHM_cb in sigmas_rel_FWHM_cb.items():
         f(xs, *par),
         ls="--",
         lw=0.5,
-        label=f"Functional fit: ${np.ceil(stochastic * 10) / 10:.1f}\% / \sqrt{{E}} \oplus {np.ceil(constant * 10) / 10:.1f}\%$",
+        label=fr"Functional fit: ${np.ceil(stochastic * 10) / 10:.1f}\% / \sqrt{{E}} \oplus {np.ceil(constant * 10) / 10:.1f}\%$",
     )
 xmin = np.min(energy_values)
 xmax = np.max(energy_values) * 1.05