diff --git a/requirements.txt b/requirements.txt
index ce8375d..99d4bb3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,7 +8,7 @@ chardet==3.0.4
 click==6.7
 docutils==0.14
 durationpy==0.5
-ecdsa==0.13
+ecdsa==0.13.3
 Flask==0.12.2
 future==0.16.0
 hjson==3.0.1