diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..a77ef71
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,5 @@
+# Pinning our toolchain ensures ./scripts/regenerate_test_rustdocs.sh always
+# emits the desired format.
+
+[toolchain]
+channel = "nightly"