diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 0d3eaf8b..5fe55160 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -6,8 +6,14 @@ build:
   os: ubuntu-lts-latest
   tools:
     python: "3.12"
-    rust: "latest"
   commands:
+    # Install a current version of rust
+    - asdf install rust 1.86.0
+    - asdf global rust 1.86.0
+
+    # proc-macro2 v1.0.95 expects at least nightly-2025-04-16.
+    - cargo update --package proc-macro2 --precise 1.0.94
+
     # Generate "book/theme/index.hbs" as "skeleton" of the generated pages.
     - book/update-theme.py
     # Install mdbook.