diff --git a/.github/workflows/big_endian.yml b/.github/workflows/big_endian.yml
new file mode 100644
index 0000000..6057f5d
--- /dev/null
+++ b/.github/workflows/big_endian.yml
@@ -0,0 +1,142 @@
+name: Big-Endian Architecture Tests
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - "quaddtype/**"
+      - ".github/workflows/**"
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  big_endian_tests:
+    runs-on: ubuntu-22.04
+    continue-on-error: true
+    strategy:
+      fail-fast: false
+      matrix:
+        BUILD_PROP:
+          - [
+              "s390x (IBM Z Big Endian)",
+              "s390x-linux-gnu",
+              "s390x/ubuntu:22.04",
+              "s390x",
+            ]
+          - [
+              "s390x - baseline(Z13)",
+              "s390x-linux-gnu",
+              "s390x/ubuntu:22.04",
+              "s390x",
+            ]
+    env:
+      ARCH_NAME: ${{ matrix.BUILD_PROP[0] }}
+      TOOLCHAIN_NAME: ${{ matrix.BUILD_PROP[1] }}
+      DOCKER_CONTAINER: ${{ matrix.BUILD_PROP[2] }}
+      ARCH: ${{ matrix.BUILD_PROP[3] }}
+      TERM: xterm-256color
+
+    name: "${{ matrix.BUILD_PROP[0] }}"
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+          fetch-tags: true
+          persist-credentials: false
+
+      - name: Initialize binfmt_misc for qemu-user-static
+        run: |
+          # Enable QEMU user-mode emulation for cross-architecture execution
+          docker run --rm --privileged tonistiigi/binfmt:qemu-v9.2.2-52 --install all
+
+      - name: Install cross-compilation toolchain
+        run: |
+          sudo apt update
+          sudo apt install -y ninja-build gcc-${TOOLCHAIN_NAME} g++-${TOOLCHAIN_NAME} gfortran-${TOOLCHAIN_NAME}
+
+      - name: Cache docker container
+        uses: actions/cache@v4
+        id: container-cache
+        with:
+          path: ~/docker_${{ matrix.BUILD_PROP[1] }}
+          key: container-quaddtype-${{ runner.os }}-${{ matrix.BUILD_PROP[1] }}-${{ matrix.BUILD_PROP[2] }}-${{ hashFiles('quaddtype/pyproject.toml') }}
+
+      - name: Create cross-compilation container
+        if: steps.container-cache.outputs.cache-hit != 'true'
+        run: |
+          docker run --platform=linux/${ARCH} --name quaddtype_container --interactive \
+            -v /:/host -v $(pwd):/workspace ${DOCKER_CONTAINER} /bin/bash -c "
+            # Update package manager and install essential tools
+            apt update &&
+            apt install -y cmake git python3 python-is-python3 python3-dev python3-pip build-essential &&
+            
+            # Create necessary symlinks for cross-compilation
+            mkdir -p /lib64 && ln -sf /host/lib64/ld-* /lib64/ || true &&
+            ln -sf /host/lib/x86_64-linux-gnu /lib/x86_64-linux-gnu || true &&
+            
+            # Link cross-compilation toolchain from host
+            rm -rf /usr/${TOOLCHAIN_NAME} && ln -sf /host/usr/${TOOLCHAIN_NAME} /usr/${TOOLCHAIN_NAME} &&
+            rm -rf /usr/lib/gcc/${TOOLCHAIN_NAME} && ln -sf /host/usr/lib/gcc-cross/${TOOLCHAIN_NAME} /usr/lib/gcc/${TOOLCHAIN_NAME} &&
+            
+            # Set up compiler symlinks
+            rm -f /usr/bin/gcc && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-gcc /usr/bin/gcc &&
+            rm -f /usr/bin/g++ && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-g++ /usr/bin/g++ &&
+            rm -f /usr/bin/gfortran && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-gfortran /usr/bin/gfortran &&
+            
+            # Set up binutils
+            rm -f /usr/bin/ar && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-ar /usr/bin/ar &&
+            rm -f /usr/bin/as && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-as /usr/bin/as &&
+            rm -f /usr/bin/ld && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-ld /usr/bin/ld &&
+            rm -f /usr/bin/ld.bfd && ln -sf /host/usr/bin/${TOOLCHAIN_NAME}-ld.bfd /usr/bin/ld.bfd &&
+            
+            # Link build tools
+            rm -f /usr/bin/ninja && ln -sf /host/usr/bin/ninja /usr/bin/ninja &&
+            rm -f /usr/local/bin/ninja && mkdir -p /usr/local/bin && ln -sf /host/usr/bin/ninja /usr/local/bin/ninja &&
+            
+            # Configure git for workspace access
+            git config --global --add safe.directory /workspace &&
+            
+            # Install Python build dependencies
+            python -m pip install --upgrade pip &&
+            python -m pip install meson>=1.3.2 meson-python wheel numpy &&
+            python -m pip install pytest pytest-run-parallel pytest-timeout &&
+            
+            # Install system dependencies for quaddtype (SLEEF dependencies)
+            apt install -y libssl-dev libfftw3-dev pkg-config
+          "
+          docker commit quaddtype_container quaddtype_container
+          mkdir -p "~/docker_${TOOLCHAIN_NAME}"
+          docker save -o "~/docker_${TOOLCHAIN_NAME}/quaddtype_container.tar" quaddtype_container
+
+      - name: Load container from cache
+        if: steps.container-cache.outputs.cache-hit == 'true'
+        run: docker load -i "~/docker_${TOOLCHAIN_NAME}/quaddtype_container.tar"
+
+      - name: Build quaddtype with cross-compilation and testing
+        run: |
+          docker run --rm --platform=linux/${ARCH} -e "TERM=xterm-256color" \
+            -v $(pwd):/workspace -v /:/host quaddtype_container \
+            /bin/script -e -q -c "/bin/bash --noprofile --norc -eo pipefail -c '
+              cd /workspace/quaddtype &&
+              echo \"Building quaddtype for ${ARCH_NAME}...\" &&
+              
+              # Set OpenMP linking for cross-compilation
+              export LDFLAGS=\"-fopenmp\" &&
+              
+              # Install quaddtype with test dependencies
+              python -m pip install .[test] -v --no-build-isolation --force-reinstall
+              
+              cd ..
+              python -m pytest -vvv --color=yes --timeout=600 --tb=short quaddtype/tests/
+            '"
diff --git a/quaddtype/numpy_quaddtype/src/dragon4.c b/quaddtype/numpy_quaddtype/src/dragon4.c
index 8e96c0b..5843141 100644
--- a/quaddtype/numpy_quaddtype/src/dragon4.c
+++ b/quaddtype/numpy_quaddtype/src/dragon4.c
@@ -1885,8 +1885,13 @@ Dragon4_PrintFloat_Sleef_quad(Sleef_quad *value, Dragon4_Options *opt)
     union {
         Sleef_quad q;
         struct {
+#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+            npy_uint64 hi;
+            npy_uint64 lo;
+#else
             npy_uint64 lo;
             npy_uint64 hi;
+#endif
         } i;
     } u;
     u.q = *value;
diff --git a/quaddtype/numpy_quaddtype/src/quaddtype_main.c b/quaddtype/numpy_quaddtype/src/quaddtype_main.c
index 734de21..b8c2bc4 100644
--- a/quaddtype/numpy_quaddtype/src/quaddtype_main.c
+++ b/quaddtype/numpy_quaddtype/src/quaddtype_main.c
@@ -33,7 +33,6 @@ py_is_longdouble_128(PyObject *self, PyObject *args)
 #ifdef SLEEF_QUAD_C
 static const Sleef_quad SMALLEST_SUBNORMAL_VALUE = SLEEF_QUAD_DENORM_MIN;
 #else
-// Use the exact same struct layout as the original buggy code
 static const union {
     struct {
 #if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
@@ -94,6 +93,7 @@ get_sleef_constant(PyObject *self, PyObject *args)
         result->value.sleef_value = SLEEF_QUAD_MIN;
     }
     else if (strcmp(constant_name, "smallest_subnormal") == 0) {
+        // or just use sleef_q(+0x0000000000000LL, 0x0000000000000001ULL, -16383);
         result->value.sleef_value = SMALLEST_SUBNORMAL_VALUE;
     }
     else if (strcmp(constant_name, "bits") == 0) {