diff --git a/pyproject.toml b/pyproject.toml
index 62d0a897..56bc3a8d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -28,7 +28,7 @@ dependencies = [
   "jinja2>=3.0.3",
   "json5",
   "jsonschema>=3.0.1",
-  "jupyter_server>=1.8,<2",
+  "jupyter_server>=1.8,<3",
   "packaging",
   "requests",
 ]
@@ -57,7 +57,8 @@ test = [
   "codecov",
   "ipykernel",
   "jupyter_server[test]",
-  "openapi_core>=0.14.2",
+  # openapi_core 0.15.0 alpha is not working
+  "openapi_core~=0.14.2",
   "openapi-spec-validator<0.5",
   "pytest>=5.3.2",
   "pytest-console-scripts",