diff --git a/README.md b/README.md
index 3a26947..d42fa1c 100644
--- a/README.md
+++ b/README.md
@@ -158,7 +158,7 @@ Transformers are great, but often times, you want to finetune them for your down
 
 ```python
 from refinery.adapter import transformers
-dataset, mapping = transformers.build_dataset(client, "headline", "__clickbait")
+dataset, mapping, index = transformers.build_classification_dataset(client, "headline", "__clickbait")
 ```
 
 From here, you can follow the [finetuning example](https://huggingface.co/docs/transformers/training) provided in the official Hugging Face documentation. A next step could look as follows:
diff --git a/refinery/adapter/transformers.py b/refinery/adapter/transformers.py
index 3269a23..31b61b3 100644
--- a/refinery/adapter/transformers.py
+++ b/refinery/adapter/transformers.py
@@ -9,7 +9,7 @@ def build_classification_dataset(
     client: Client,
     sentence_input: str,
     classification_label: str,
-    num_train: Optional[int] = 100,
+    num_train: Optional[int] = None,
 ):
     """Build a classification dataset from a refinery client and a config string useable for HuggingFace finetuning.