diff --git a/src/transformers/generation_utils.py b/src/transformers/generation_utils.py
index 380eec07270c9c..27b392a23d56da 100644
--- a/src/transformers/generation_utils.py
+++ b/src/transformers/generation_utils.py
@@ -953,7 +953,7 @@ def generate(
         forced_eos_token_id: Optional[int] = None,
         remove_invalid_values: Optional[bool] = None,
         synced_gpus: Optional[bool] = False,
-        exponential_decay_length_penalty: Optional[Tuple[Union[int, float]]] = None,
+        exponential_decay_length_penalty: Optional[Tuple[int, float]] = None,
         suppress_tokens: Optional[List[int]] = None,
         begin_suppress_tokens: Optional[List[int]] = None,
         forced_decoder_ids: Optional[List[int]] = None,