diff --git a/test.py b/test.py
index 4ed93b17..40f9faf9 100644
--- a/test.py
+++ b/test.py
@@ -47,7 +47,7 @@ def test(
     dataset = LoadImagesAndLabels(test_path, img_size=img_size)
     dataloader = DataLoader(dataset,
                             batch_size=batch_size,
-                            num_workers=0,
+                            num_workers=4,
                             pin_memory=False,
                             collate_fn=dataset.collate_fn)
 
@@ -67,7 +67,8 @@ def test(
         # Per image
         for si, pred in enumerate(output):
             labels = targets[targets[:, 0] == si, 1:]
-            correct, detected, tcls = [], [], []
+            correct, detected = [], []
+            tcls = torch.Tensor()
             seen += 1
 
             if pred is None:
@@ -93,8 +94,8 @@ def test(
                 correct.extend([0] * len(pred))
             else:
                 # Extract target boxes as (x1, y1, x2, y2)
-                tbox = xywh2xyxy(labels[:, 1:5]) * img_size
-                tcls = labels[:, 0].cpu()
+                tbox = xywh2xyxy(labels[:, 1:5]) * img_size  # target boxes
+                tcls = labels[:, 0]  # target classes
 
                 for *pbox, pconf, pcls_conf, pcls in pred:
                     if pcls not in tcls:
@@ -112,7 +113,7 @@ def test(
                         correct.append(0)
 
             # Append Statistics (correct, conf, pcls, tcls)
-            stats.append((correct, pred[:, 4].cpu(), pred[:, 6].cpu(), tcls))
+            stats.append((correct, pred[:, 4].cpu(), pred[:, 6].cpu(), tcls.cpu()))
 
     # Compute means
     stats_np = [np.concatenate(x, 0) for x in list(zip(*stats))]