diff --git a/tools/email-viewer/requirements.txt b/tools/email-viewer/requirements.txt
index 145e30200..a1e2f8a25 100644
--- a/tools/email-viewer/requirements.txt
+++ b/tools/email-viewer/requirements.txt
@@ -1,4 +1,4 @@
-Flask==0.10.1
+Flask==1.0
 Jinja2==2.7.2
 MarkupSafe==0.18
 Werkzeug==0.9.4