diff --git a/requirements.txt b/requirements.txt
index a257e29..2a2c597 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,4 +4,4 @@
 # in `lib/` subdirectory.
 #
 # Note: The `lib` directory is added to `sys.path` by `appengine_config.py`.
-Flask==0.10
+Flask==1.0