diff --git a/README.md b/README.md
index 433c166c3f2..b88530961f9 100644
--- a/README.md
+++ b/README.md
@@ -85,9 +85,23 @@ Use [`codespell`](https://github.com/codespell-project/codespell) to check for c
   nox -s spelling -- -w -i 3
   ```
 
+## Dependency files
+
+`nox` sessions use dependencies from requirements files in the `tests/` directory.
+Each session has a `tests/{name}.in` file with direct dependencies and a lock file in `tests/{name}.txt` that pins *exact versions* for both direct and transitive dependencies.
+The lock files contain tested dependencies that are automatically updated on a weekly basis.
+
+If you'd like to use untested dependencies, set `PINNED=false` as in the following example:
+
+```
+PINNED=false nox -s "checkers(docs-build)"
+```
+
+For more details about using unpinned and tested dependencies for doc builds, see [Setting up your environment to build documentation locally](https://docs.ansible.com/ansible/latest/community/documentation_contributions.html#setting-up-your-environment-to-build-documentation-locally).
+
 ## Updating dependencies
 
-Use the following `nox` session to update project dependency versions.
+Use the following `nox` session to update the dependency lock files in `tests/`.
 
   ```
   nox -e pip-compile
diff --git a/noxfile.py b/noxfile.py
index ce660aee35f..2f6df57159d 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -18,7 +18,9 @@
 
 def install(session: nox.Session, *args, req: str, **kwargs):
     if PINNED:
-        kwargs.setdefault("env", {})["PIP_CONSTRAINT"] = f"tests/{req}.txt"
+        pip_constraint = f"tests/{req}.txt"
+        kwargs.setdefault("env", {})["PIP_CONSTRAINT"] = pip_constraint
+        session.log(f"export PIP_CONSTRAINT={pip_constraint!r}")
     session.install("-r", f"tests/{req}.in", *args, **kwargs)