diff --git a/test.py b/test.py
index c9516953fc..df06fe2903 100644
--- a/test.py
+++ b/test.py
@@ -128,12 +128,13 @@ def test(
                         continue
 
                     # Best iou, index between pred and targets
-                    iou, bi = bbox_iou(pbox, tbox).max(0)
+                    m = (pcls == tcls_tensor).nonzero().view(-1)
+                    iou, bi = bbox_iou(pbox, tbox[m]).max(0)
 
                     # If iou > threshold and class is correct mark as correct
-                    if iou > iou_thres and bi not in detected:  # and pcls == tcls[bi]:
+                    if iou > iou_thres and m[bi] not in detected:  # and pcls == tcls[bi]:
                         correct[i] = 1
-                        detected.append(bi)
+                        detected.append(m[bi])
 
             # Append statistics (correct, conf, pcls, tcls)
             stats.append((correct, pred[:, 4].cpu(), pred[:, 6].cpu(), tcls))