diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 8303409..9db55a8 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -5,14 +5,13 @@
 version: 2
 
 # Set the version of Python and other tools you might need
+# ubuntu-20.04 was removed as a build image, which fails the build outright rather than
+# falling back. Read the Docs supports ubuntu-22.04, ubuntu-24.04, ubuntu-26.04 and
+# ubuntu-lts-latest; pin a real version so an image being retired is a deliberate bump.
 build:
-  os: ubuntu-20.04
+  os: ubuntu-24.04
   tools:
-    python: "3.10"
-    # You can also specify other tool versions:
-    # nodejs: "16"
-    # rust: "1.55"
-    # golang: "1.17"
+    python: "3.12"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx: