diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 37db848558..2a0610cf03 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ env:
   CARGO_PROFILE_TEST_DEBUG: 0
   CARGO_PROFILE_DEV_DEBUG: 0
   # If nightly is breaking CI, modify this variable to target a specific nightly version.
-  NIGHTLY_TOOLCHAIN: nightly
+  NIGHTLY_TOOLCHAIN: nightly-2025-05-16 # pinned until a fix for https://github.com/rust-lang/miri/issues/4323 is released
   RUSTFLAGS: "-D warnings"
   BINSTALL_VERSION: "v1.12.3"