diff --git a/rfdetr/engine.py b/rfdetr/engine.py
index cb589dfa..693bcfbf 100644
--- a/rfdetr/engine.py
+++ b/rfdetr/engine.py
@@ -185,7 +185,7 @@ def coco_extended_metrics(coco_eval):
 
     iou_thrs, rec_thrs = coco_eval.params.iouThrs, coco_eval.params.recThrs
     iou50_idx, area_idx, maxdet_idx = (
-        int(np.argwhere(np.isclose(iou_thrs, 0.50))), 0, 2)
+        int(np.argmax(np.isclose(iou_thrs, 0.50))), 0, 2)
 
     P = coco_eval.eval["precision"]
     S = coco_eval.eval["scores"]
@@ -338,4 +338,4 @@ def evaluate(model, criterion, postprocess, data_loader, base_ds, device, args=N
         if "segm" in iou_types:
             results_json = coco_extended_metrics(coco_evaluator.coco_eval["segm"])
             stats["coco_eval_masks"] = coco_evaluator.coco_eval["segm"].stats.tolist()
-    return stats, coco_evaluator
\ No newline at end of file
+    return stats, coco_evaluator