diff --git a/requirements.txt b/requirements.txt
index 098b2e1..b2a9fc9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,7 +4,7 @@
 # in `lib/` subdirectory.
 #
 # Note: The `lib` directory is added to `sys.path` by `appengine_config.py`.
-Flask==0.12.2
+Flask==1.0
 simplejson==3.6.5
 pytz==2014.9
 google-api-python-client==1.3.1