diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 48763213690..ce13647fa58 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -74,6 +74,7 @@ jobs:
           else
             RUSTC_HASH=$(< rust-version)
           fi
+          # We need a nightly cargo for parts of the cargo miri test suite.
           rustup-toolchain-install-master \
             -f \
             -n master "$RUSTC_HASH" \