diff --git a/pyproject.toml b/pyproject.toml
index 0c849b308530b7b0fd2e4467443eff8085e40cff..5d8f837064e84df04fae883feacfb3f5a84f6499 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,7 +35,7 @@ graphql-core = "^3.1.2"
 websocket-client = "^0.57"
 
 [tool.poetry.dev-dependencies]
-black = "^20.8b1"
+black = {version = "^20.8b1", allow-prereleases = true}
 mypy = "^0.790"
 pylint = "^2.7.2"
 sphinx = "^3.2.1"