diff --git a/templates/github/.github/workflows/build.yml.j2 b/templates/github/.github/workflows/build.yml.j2
index d9f619b9..25119d02 100644
--- a/templates/github/.github/workflows/build.yml.j2
+++ b/templates/github/.github/workflows/build.yml.j2
@@ -37,7 +37,7 @@ jobs:
           uvx twine check dist/*
       - name: "Install built packages"
         run: |
-          uv run --script .ci/scripts/calc_constraints.py -u pyproject.toml > upperbounds_constraints.txt
+          uv run --script .ci/scripts/calc_constraints.py -u {% if setup_py -%} requirements.txt {% else -%} pyproject.toml {% endif -%} > upperbounds_constraints.txt
           # This seems to be the only way to inject the constraints file.
           uv pip install dist/{{ plugin_name | snake }}-*-py3-none-any.whl -c .ci/assets/ci_constraints.txt -c upperbounds_constraints.txt
       - name: "Generate api specs"