diff --git a/pyproject.toml b/pyproject.toml
index 8e6df2c..0464be4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,6 +38,7 @@ requires-python = ">=3.8"
 dependencies = [
     "alembic >=1.12.1, < 2.0.0",
     "fastapi >= 0.87.0",
+    "gunicorn >= 21.2.0",
     "ical-library >= 0.1.0",
     "itsdangerous >= 2.1.2",
     "pendulum >= 2.0.0,<3.0.0",