diff --git a/requirements.txt b/requirements.txt
index 0d5921a..f60a427 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,7 +44,7 @@ jws==0.1.3
 MarkupSafe==1.1.1
 ndg-httpsclient==0.5.1
 nexmo==2.4.0
-nltk==3.4.4
+nltk==3.6.3
 num2words==0.5.10
 numpy==1.17.0
 oauth2client==3.0.0
diff --git a/test.txt b/test.txt
index fc39f8d..f13b052 100644
--- a/test.txt
+++ b/test.txt
@@ -44,7 +44,7 @@ jws==0.1.3
 MarkupSafe==1.1.1
 ndg-httpsclient==0.5.1
 nexmo==2.4.0
-nltk==3.4.4
+nltk==3.6.3
 num2words==0.5.10
 numpy==1.17.0
 oauth2client==3.0.0