diff --git a/opf/_eval/data.py b/opf/_eval/data.py
index a15d0f4..fc241b1 100644
--- a/opf/_eval/data.py
+++ b/opf/_eval/data.py
@@ -75,7 +75,7 @@ def iter_json_records(dataset_path: str) -> Iterator[Mapping[str, object]]:
         raise ValueError("Dataset path must be local filesystem only (no URI schemes).")
     if "*" in dataset_path:
         file_paths = sorted(glob.glob(dataset_path))
-    elif os.path.exists(dataset_path):
+    elif os.path.isfile(dataset_path):
         file_paths = [dataset_path]
     else:
         file_paths = sorted(glob.glob(f"{dataset_path.rstrip('/')}/*.gz"))