diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 491c023c8..682132e73 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -41,7 +41,7 @@ jobs:
       - name: Setup Rust toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2025-01-07 # pin to working nightly
           components: llvm-tools-preview
       - name: Install cargo-nextest
         uses: taiki-e/install-action@cargo-nextest
@@ -101,7 +101,7 @@ jobs:
       - name: Setup Rust toolchain
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2025-01-07 # pin to working nightly
           components: llvm-tools-preview
       - name: Install cargo-nextest
         uses: taiki-e/install-action@cargo-nextest