diff --git a/demo/api/requirements.txt b/demo/api/requirements.txt
index 5f26b9e..3bb0d23 100644
--- a/demo/api/requirements.txt
+++ b/demo/api/requirements.txt
@@ -14,7 +14,7 @@ Keras-Preprocessing==1.0.9
 Markdown==3.0.1
 MarkupSafe==1.1.1
 mock==2.0.0
-nltk==3.4
+nltk==3.4.5
 numpy==1.16.2
 pbr==5.1.3
 protobuf==3.7.0