diff --git a/requirements.txt b/requirements.txt
index ff1ba3c3..37e68e9d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,4 +3,4 @@ PyYAML>=4.2b1
 python-http-client>=3.2.1
 six==1.11.0
 pytest==3.8.2
-starkbank-ecdsa>=1.0.0
+starkbank-ecdsa>=1.0.0,<2.0.0