diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4d708201d3c..22f388698f0 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -49,10 +49,12 @@ jobs:
         run: |
           rustup target add thumbv7m-none-eabi
           sudo apt-get -y install gcc-arm-none-eabi
+          sudo apt-get clean
       - name: shellcheck the CI and `contrib` scripts
         if: "matrix.platform == 'ubuntu-latest'"
         run: |
           sudo apt-get -y install shellcheck
+          sudo apt-get clean
           shellcheck ci/*.sh -aP ci
           shellcheck contrib/*.sh -aP contrib
       - name: Set RUSTFLAGS to deny warnings
@@ -260,6 +262,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get -y install build-essential binutils-dev libunwind-dev
+          sudo apt-get clean
       - name: Pin the regex dependency
         run: |
           cd fuzz && cargo update -p regex --precise "1.9.6" --verbose
diff --git a/fuzz/ci-fuzz.sh b/fuzz/ci-fuzz.sh
index bae03bebc54..e3bb1910b2c 100755
--- a/fuzz/ci-fuzz.sh
+++ b/fuzz/ci-fuzz.sh
@@ -18,13 +18,14 @@ export RUSTFLAGS="--cfg=secp256k1_fuzz --cfg=hashes_fuzz"
 mkdir -p hfuzz_workspace/full_stack_target/input
 pushd write-seeds
 RUSTFLAGS="$RUSTFLAGS --cfg=fuzzing" cargo run ../hfuzz_workspace/full_stack_target/input
+cargo clean
 popd
 
 cargo install --color always --force honggfuzz --no-default-features
+
 # Because we're fuzzing relatively few iterations, the maximum possible
-# compiler optimizations aren't necessary, so switch to defaults.
+# compiler optimizations aren't necessary, so we turn off LTO
 sed -i 's/lto = true//' Cargo.toml
-sed -i 's/codegen-units = 1//' Cargo.toml
 
 export HFUZZ_BUILD_ARGS="--features honggfuzz_fuzz"