diff --git a/requirements.txt b/requirements.txt
index b227dd1..70b4533 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 click==6.6
-ecdsa==0.13
+ecdsa==0.13.3
 Flask==1.0
 future==0.15.2
 itsdangerous==0.24