diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 395fe42b..8eb5cb3d 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -14,11 +14,8 @@ sphinx:
 
 python:
   install:
-    # pip install kauldron[docs] fail: https://github.com/pypa/pip/issues/13092
+    # `pip install .[docs]` fail: https://github.com/pypa/pip/issues/13092
     # So try to install the dependencies separately.
-    - method: pip
-      path: sphinx-apitree
-      extra_requirements:
-        - ext
+    - requirements: docs/requirements.txt
     - method: pip
       path: .
diff --git a/docs/requirements.txt b/docs/requirements.txt
new file mode 100644
index 00000000..f20275b9
--- /dev/null
+++ b/docs/requirements.txt
@@ -0,0 +1 @@
+sphinx-apitree[ext]