diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
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--- /dev/null
+++ b/rust-toolchain.toml
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+# This file pins the toolchain  so that ./scripts/regenerate_test_rustdocs.sh
+# always produces the desired format. Every new nightly release, if the rustdoc
+# format is unchanged, this toolchain may be incremented. Otherwise we need a new
+# version of the adapter.
+
+[toolchain]
+channel = "nightly-2024-01-09"
+