diff --git a/scripts/code_summarization/requirements.txt b/scripts/code_summarization/requirements.txt
index e984be6db..b3cbf13e4 100644
--- a/scripts/code_summarization/requirements.txt
+++ b/scripts/code_summarization/requirements.txt
@@ -1,4 +1,4 @@
-nltk==3.4.5
+nltk==3.6.6
 numpy==1.15.4
 scikit_learn==0.20.2
 torch==1.0.0