diff --git a/clip_retrieval/clip_inference/reader.py b/clip_retrieval/clip_inference/reader.py
index e49aa4d..f9bc98a 100644
--- a/clip_retrieval/clip_inference/reader.py
+++ b/clip_retrieval/clip_inference/reader.py
@@ -194,7 +194,7 @@ def collate_fn(batch):
         shuffle=False,
         num_workers=num_prepro_workers,
         pin_memory=True,
-        prefetch_factor=2,
+        prefetch_factor=2 if num_prepro_workers>0 else None,
         collate_fn=collate_fn if input_format == "files" else None,
     )
     return data