diff --git a/.github/actions/rust/action.yml b/.github/actions/rust/action.yml
index c2f1eff9e5..97718b393d 100644
--- a/.github/actions/rust/action.yml
+++ b/.github/actions/rust/action.yml
@@ -47,7 +47,6 @@ runs:
         if [ "$(apt-cache search --names-only '^mold$' | wc -l)" -ge 1 ]; then
           [ "$APT_UPDATED" ] || sudo apt-get update && echo "APT_UPDATED=1" >> "$GITHUB_ENV"
           sudo apt-get install -y --no-install-recommends mold
-          echo "RUSTFLAGS=-C link-arg=-fuse-ld=mold $RUSTFLAGS" >> "$GITHUB_ENV"
         fi
 
     # See https://corrode.dev/blog/tips-for-faster-ci-builds/
@@ -57,9 +56,11 @@ runs:
         {
           echo "CARGO_PROFILE_RELEASE_LTO=true"
           echo "CARGO_PROFILE_RELEASE_CODEGEN_UNITS=1"
-          if [ "${{ runner.os }}" == "Windows"]; then
-              echo "RUSTFLAGS=-C link-arg=-fuse-ld=lld $RUSTFLAGS"
-            fi
+          if [[ "${{ runner.os }}" == "Linux" && "$(command -v mold)" ]]; then
+            echo "RUSTFLAGS=-C linker=clang -C link-arg=-fuse-ld=mold $RUSTFLAGS"
+          elif [[ "${{ runner.os }}" == "Windows" ]]; then
+            echo "RUSTFLAGS=-C link-arg=-fuse-ld=lld $RUSTFLAGS"
+          fi
         } >> "$GITHUB_ENV"
 
     - name: Enable sscache
diff --git a/.github/workflows/bench.yml b/.github/workflows/bench.yml
index 40ebbbb86d..d73ab48ab5 100644
--- a/.github/workflows/bench.yml
+++ b/.github/workflows/bench.yml
@@ -12,7 +12,7 @@ env:
   PERF_OPT: record -F997 --call-graph fp -g
   SCCACHE_CACHE_SIZE: 128G
   SCCACHE_DIRECT: true
-  MTU: 1504
+  MTU: 1504 # https://github.com/microsoft/msquic/issues/4618
 
 permissions:
   contents: read
@@ -52,8 +52,6 @@ jobs:
       - name: Set PATH and environment
         run: |
           echo "/home/bench/.cargo/bin" >> "${GITHUB_PATH}"
-          # Append to RUSTFLAGS, which may already be set by the Rust action.
-          echo "RUSTFLAGS=-C link-arg=-Wl,--no-rosegment, -C force-frame-pointers=yes $RUSTFLAGS" >> "$GITHUB_ENV"
 
       - name: Install Rust
         uses: ./.github/actions/rust
@@ -75,6 +73,8 @@ jobs:
       - name: Build neqo
         run: |
           cargo "+$TOOLCHAIN" bench --workspace --features bench --no-run
+          # See https://github.com/flamegraph-rs/flamegraph for why we append to RUSTFLAGS here.
+          export RUSTFLAGS="-C link-arg=-Wl,--no-rosegment, -C force-frame-pointers=yes $RUSTFLAGS"
           cargo "+$TOOLCHAIN" build --locked --release --bin neqo-client --bin neqo-server
 
       - name: Build msquic