diff --git a/fiftyone/utils/eval/coco.py b/fiftyone/utils/eval/coco.py
index 26e3642201..8ac3f87be6 100644
--- a/fiftyone/utils/eval/coco.py
+++ b/fiftyone/utils/eval/coco.py
@@ -830,6 +830,8 @@ def _compute_pr_curves(samples, config, classes=None, progress=None):
             thresholds[idx][c_idx] = t
             if rec.size != 0:
                 recall_sweep[idx][c_idx] = rec[-1]
+            else:
+                recall_sweep[idx][c_idx] = 0               
 
     return precision, recall, thresholds, iou_threshs, classes, recall_sweep