diff --git a/requirements.txt b/requirements.txt
index daea083..f55b204 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-nltk==3.4.5
+nltk==3.9
 JPype1==1.1.2
 snowballstemmer==1.2.1
 nlptoolkit-MorphologicalAnalysis==1.0.44