diff --git a/minillm/transformers/examples/research_projects/decision_transformer/requirements.txt b/minillm/transformers/examples/research_projects/decision_transformer/requirements.txt
index 2d510dde..27993ec3 100644
--- a/minillm/transformers/examples/research_projects/decision_transformer/requirements.txt
+++ b/minillm/transformers/examples/research_projects/decision_transformer/requirements.txt
@@ -115,7 +115,7 @@ mujoco-py==2.1.2.14
 multidict==6.0.2
 multiprocess==0.70.12.2
 mypy-extensions==0.4.3
-nltk==3.7
+nltk==3.9
 numba==0.55.1
 numpy==1.22.3
 oauthlib==3.2.2