diff --git a/.readthedocs.yml b/.readthedocs.yml
new file mode 100644
index 000000000..f694065a8
--- /dev/null
+++ b/.readthedocs.yml
@@ -0,0 +1,6 @@
+# syntax: https://docs.readthedocs.io/en/latest/yaml-config.html
+
+formats:
+    - pdf
+
+requirements_file: docs/requirements-docs.txt
diff --git a/docs/requirements-docs.txt b/docs/requirements-docs.txt
index 3151e8296..bf600ea5e 100644
--- a/docs/requirements-docs.txt
+++ b/docs/requirements-docs.txt
@@ -1,3 +1,3 @@
-sphinx
+sphinx>=1.5.4
 sphinx_rtd_theme
 sphinx-pypi-upload