diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d3b00019..c6417a03 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -157,6 +157,8 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@miri
+        with:
+          toolchain: nightly-2025-05-16  # https://github.com/rust-lang/miri/issues/4323
       - run: cargo miri setup
       - run: cd serde && cargo miri test --features derive,rc,unstable
         env: