diff --git a/utils/metrics.py b/utils/metrics.py
index 4f1b5e2d2c2d..2e0e0c65e63d 100644
--- a/utils/metrics.py
+++ b/utils/metrics.py
@@ -71,6 +71,8 @@ def ap_per_class(tp, conf, pred_cls, target_cls, plot=False, save_dir='.', names
 
     # Compute F1 (harmonic mean of precision and recall)
     f1 = 2 * p * r / (p + r + 1e-16)
+    names = [v for k, v in names.items() if k in unique_classes]  # list: only classes that have data
+    names = {i: v for i, v in enumerate(names)}  # to dict
     if plot:
         plot_pr_curve(px, py, ap, Path(save_dir) / 'PR_curve.png', names)
         plot_mc_curve(px, f1, Path(save_dir) / 'F1_curve.png', names, ylabel='F1')