diff --git a/val.py b/val.py
index 36f2a6c0284b..13971612ac78 100644
--- a/val.py
+++ b/val.py
@@ -155,7 +155,7 @@ def run(
     # Configure
     model.eval()
     cuda = device.type != 'cpu'
-    is_coco = isinstance(data.get('val'), str) and data['val'].endswith('coco/val2017.txt')  # COCO dataset
+    is_coco = isinstance(data.get('val'), str) and data['val'].endswith(f'coco{os.sep}val2017.txt')  # COCO dataset
     nc = 1 if single_cls else int(data['nc'])  # number of classes
     iouv = torch.linspace(0.5, 0.95, 10, device=device)  # iou vector for mAP@0.5:0.95
     niou = iouv.numel()