diff --git a/ultralytics/data/dataset.py b/ultralytics/data/dataset.py
index 575243f..1d13261 100644
--- a/ultralytics/data/dataset.py
+++ b/ultralytics/data/dataset.py
@@ -126,6 +126,7 @@ class YOLODataset(BaseDataset):
         # Read cache
         [cache.pop(k) for k in ('hash', 'version', 'msgs')]  # remove items
         labels = cache['labels']
+        assert len(labels), f'No valid labels found, please check your dataset. {HELP_URL}'
         self.im_files = [lb['im_file'] for lb in labels]  # update im_files
 
         # Check if the dataset is all boxes or all segments
diff --git a/ultralytics/data/utils.py b/ultralytics/data/utils.py
index 561b994..807ddad 100644
--- a/ultralytics/data/utils.py
+++ b/ultralytics/data/utils.py
@@ -24,7 +24,7 @@ from ultralytics.utils.checks import check_file, check_font, is_ascii
 from ultralytics.utils.downloads import download, safe_download, unzip_file
 from ultralytics.utils.ops import segments2boxes
 
-HELP_URL = 'See https://docs.ultralytics.com/yolov5/tutorials/train_custom_data'
+HELP_URL = 'See https://docs.ultralytics.com/datasets/detect for YOLO dataset format help.'
 IMG_FORMATS = 'bmp', 'dng', 'jpeg', 'jpg', 'mpo', 'png', 'tif', 'tiff', 'webp', 'pfm'  # image suffixes
 VID_FORMATS = 'asf', 'avi', 'gif', 'm4v', 'mkv', 'mov', 'mp4', 'mpeg', 'mpg', 'ts', 'wmv', 'webm'  # video suffixes
 PIN_MEMORY = str(os.getenv('PIN_MEMORY', True)).lower() == 'true'  # global pin_memory for dataloaders