diff --git a/requirements.txt b/requirements.txt
index ad634df..5ff3a0e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@ certifi==2018.10.15
 chardet==3.0.4
 codecov==2.0.15
 coverage==4.5.1
-ecdsa==0.13
+ecdsa==0.13.3
 fastecdsa==1.6.5
 idna==2.7
 more-itertools==4.3.0