diff --git a/pyproject.toml b/pyproject.toml
index 393b51d..0f5bb8b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,5 +31,5 @@ pytest-cov = "~2.7"
 responses = "~0.10"
 
 [build-system]
-requires = ["poetry>=0.12"]
+requires = ["poetry==1.0","cryptography==2.7"]
 build-backend = "poetry.masonry.api"