diff --git a/contrib/zclassic/requirements.txt b/contrib/zclassic/requirements.txt
index 5cb8a59b..3911b9d4 100644
--- a/contrib/zclassic/requirements.txt
+++ b/contrib/zclassic/requirements.txt
@@ -1,7 +1,7 @@
 certifi==2017.11.5
 chardet==3.0.4
 dnspython==1.15.0
-ecdsa==0.13
+ecdsa==0.13.3
 idna==2.6
 jsonrpclib-pelix==0.3.1
 pbkdf2==1.3