diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 834a524f6..b993c518f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -308,13 +308,20 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Install Rust toolchain
-        uses: dtolnay/rust-toolchain@nightly
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: nightly-2025-01-24
+          # Pinning to specific nightly build for now. More recent versions
+          # (not sure of start date) cause linker problems with OpenSSL native
+          # code on Mac and Windows, but only when built with minimal dependencies.
+          # Problem discovered on 2025-01-27.
+          # TO DO: Investigate and file bugs if necessary against rust-lang.
 
       - name: Cache Rust dependencies
         uses: Swatinem/rust-cache@v2
 
       - name: Run tests
-        run: cargo +nightly test -Z direct-minimal-versions --all-targets --all-features
+        run: cargo +nightly-2025-01-24 test -Z direct-minimal-versions --all-targets --all-features
 
   clippy_check:
     name: Clippy