diff --git a/pyproject.toml b/pyproject.toml
index d5f3803..6b90e54 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -64,7 +64,7 @@ mypy = "==1.8.0"
 optional = true
 
 [tool.poetry.group.contract-tests.dependencies]
-Flask = "3.0.0"
+Flask = "<4"
 requests = ">=2.31.0"
 urllib3 = ">=1.22.0,<3"