diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index ddcc4130d5f75d482897fbd94976564a3e2e129a..1e672adf14934f21e4db05b64a3cc853b1a7253f 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -1736,10 +1736,8 @@ obtain profiles::
       ForceCommand BST_PROFILE=artifact-receive cd /tmp && bst-artifact-receive --pull-url https://example.com/ /home/artifacts/artifacts
 
 
-The MANIFEST.in and setup.py
-----------------------------
-When adding a dependency to BuildStream, it's important to update the setup.py accordingly.
-
+Managing data files
+-------------------
 When adding data files which need to be discovered at runtime by BuildStream, update setup.py accordingly.
 
 When adding data files for the purpose of docs or tests, or anything that is not covered by
@@ -1749,3 +1747,23 @@ At any time, running the following command to create a source distribution shoul
 creating a tarball which contains everything we want it to include::
 
   ./setup.py sdist
+
+
+Updating BuildStream's Python dependencies
+------------------------------------------
+BuildStream's Python dependencies are listed in multiple
+`requirements files <https://pip.readthedocs.io/en/latest/reference/pip_install/#requirements-file-format>`
+present in the ``requirements`` directory.
+
+All ``.txt`` files in this directory are generated from the corresponding
+``.in`` file, and each ``.in`` file represents a set of dependencies. For
+example, ``requirements.in`` contains all runtime dependencies of BuildStream.
+``requirements.txt`` is generated from it, and contains pinned versions of all
+runtime dependencies (including transitive dependencies) of BuildStream.
+
+When adding a new dependency to BuildStream, or updating existing dependencies,
+it is important to update the appropriate requirements file accordingly. After
+changing the ``.in`` file, run the following to update the matching ``.txt``
+file::
+
+   make -C requirements
diff --git a/requirements/Makefile b/requirements/Makefile
index 4f966254f7292f308aa356bb853d4be91a6d0c95..c49a2e2d087f76cd95a092e3c64597c6805dffb7 100644
--- a/requirements/Makefile
+++ b/requirements/Makefile
@@ -14,7 +14,7 @@ VENV_PIP = $(VENVDIR)/bin/pip
 all: $(REQUIREMENTS_TXT)
 
 %.txt: %.in
-	$(eval VENVDIR := $(shell mktemp -d $$TMPDIR/bst-venv.XXXXXX))
+	$(eval VENVDIR := $(shell mktemp -d $(CURDIR)/.bst-venv.XXXXXX))
 	$(VENV) $(VENVDIR)
 	$(VENV_PIP) install -r $^
 	$(VENV_PIP) freeze -r $^ > $@