diff --git a/.github/workflows/build_dev_wheels.yml b/.github/workflows/build_dev_wheels.yml
index 38af741f..871e8f50 100644
--- a/.github/workflows/build_dev_wheels.yml
+++ b/.github/workflows/build_dev_wheels.yml
@@ -51,16 +51,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        # _Unsupported_ macOS-10.x
-        # - os: macos-10.15
-        #   build: "cp3*-macosx_x86_64"
-        #   name: macOS (10.9)
-        #   target: '10.9'
-        #   flags: CC=gcc-11 CXX=g++-11 CXXFLAGS="-static-libgcc -static-libstdc++"
         # Supported macOS-10.x
         - os: macos-10.15
           build: "cp3*-macosx_x86_64"
-          # build: "cp3*-macosx_arm64 cp3*-macosx_x86_64"
           name: macOS (10.15+)
           target: '10.15'
         # macOS-11
@@ -169,23 +162,19 @@ jobs:
         with:
             arch: ${{ matrix.arch }}
 
-      - name: Set Windows variables
-        if: runner.os == 'Windows'
-        shell: bash
-        run: |
-          echo "CC=cl.exe" >> $GITHUB_ENV
-          echo "CXX=cl.exe" >> $GITHUB_ENV
-
       - name: Build wheels
         uses: pypa/cibuildwheel@v2.1.1
         env:
           CIBW_BUILD: ${{ matrix.build }}
-          CIBW_ARCHS: all 
-          CIBW_ENVIRONMENT: "${{ matrix.flags }} TWEEDLEDUM_DEV_VERSION=${{needs.setup_date.outputs.timestamp}}"
+          CIBW_ARCHS: all
+          CIBW_ENVIRONMENT_LINUX: "TWEEDLEDUM_DEV_VERSION=${{needs.setup_date.outputs.timestamp}}"
+          CIBW_ENVIRONMENT_MACOS: "${{ matrix.flags }} _PYTHON_HOST_PLATFORM=macosx-${{ matrix.target }}-x86_64"
+          CIBW_ENVIRONMENT_WINDOWS: "CC=cl.exe CXX=cl.exe"
           CIBW_TEST_REQUIRES: pytest
           CIBW_TEST_COMMAND: pytest --import-mode importlib -v {project}/python/test/
           CMAKE_BUILD_PARALLEL_LEVEL: 2
           MACOSX_DEPLOYMENT_TARGET: ${{ matrix.target }}
+          TWEEDLEDUM_DEV_VERSION: ${{needs.setup_date.outputs.timestamp}}
 
       - name: Upload built wheels
         uses: actions/upload-artifact@v2
diff --git a/.github/workflows/build_wheels.yml b/.github/workflows/build_wheels.yml
index 3e4f2ffc..17ad3b6f 100644
--- a/.github/workflows/build_wheels.yml
+++ b/.github/workflows/build_wheels.yml
@@ -41,16 +41,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        # _Unsupported_ macOS-10.x
-        # - os: macos-10.15
-        #   build: "cp3*-macosx_x86_64"
-        #   name: macOS (10.9)
-        #   target: '10.9'
-        #   flags: CC=gcc-11 CXX=g++-11 CXXFLAGS="-static-libgcc -static-libstdc++"
         # Supported macOS-10.x
         - os: macos-10.15
           build: "cp3*-macosx_x86_64"
-          # build: "cp3*-macosx_arm64 cp3*-macosx_x86_64"
           name: macOS (10.15+)
           target: '10.15'
         # macOS-11
@@ -159,19 +152,13 @@ jobs:
         with:
             arch: ${{ matrix.arch }}
 
-      - name: Set Windows variables
-        if: runner.os == 'Windows'
-        shell: bash
-        run: |
-          echo "CC=cl.exe" >> $GITHUB_ENV
-          echo "CXX=cl.exe" >> $GITHUB_ENV
-
       - name: Build wheels
         uses: pypa/cibuildwheel@v2.1.1
         env:
           CIBW_BUILD: ${{ matrix.build }}
-          CIBW_ARCHS: all 
-          CIBW_ENVIRONMENT: "${{ matrix.flags }}"
+          CIBW_ARCHS: all
+          CIBW_ENVIRONMENT_MACOS: "${{ matrix.flags }} _PYTHON_HOST_PLATFORM=macosx-${{ matrix.target }}-x86_64"
+          CIBW_ENVIRONMENT_WINDOWS: "CC=cl.exe CXX=cl.exe"
           CIBW_TEST_REQUIRES: pytest
           CIBW_TEST_COMMAND: pytest --import-mode importlib -v {project}/python/test/
           CMAKE_BUILD_PARALLEL_LEVEL: 2
diff --git a/README.md b/README.md
index a567dfb9..852d2dc4 100644
--- a/README.md
+++ b/README.md
@@ -53,9 +53,11 @@ passes in python.
 
 # Installation
 
-Tweedledum has two python packages that can be installed using `pip`.  For both,
-you will at least __Python 3.6__.  The `tweedledum` package contains the latest
-stable release.  You can install it from PyPI using:
+[Known issues](#known-issues) with _macOS High Sierra (10.13)_ and _macOS Mojave (10.14)_.
+
+`tweedledum` has two python packages that can be installed using `pip`.  For
+both, you will at least __Python 3.6__.  The `tweedledum` package contains the
+latest stable release.  You can install it from PyPI using:
 
 * Latest stable release (Linux/Mac/Windows)
 
@@ -185,6 +187,26 @@ third-party tools and services. Thanks a lot!
 - [**pybind11**](https://github.com/pybind/pybind11) - Seamless operability between C++11 and Python
 - [**rang**](https://github.com/agauniyal/rang) - A Minimal, Header only Modern c++ library for terminal goodies
 
+## Known issues
+
+These are issues that hopefully will be fixed, but currently are unsolved.  If
+you know how to help with one of these issues, contributions are welcome!
+
+### macOS: High Sierra (10.13) and Mojave (10.14)
+
+`tweedledum` offers limited support for both systems.  While wheels might be
+available for some releases, it is strongly advised to install `tweedledum` or
+`tweedledum-dev` by building them directly from source.  For example:
+
+```sh
+CC=gcc-10 CXX=g++-10 CXXFLAGS="-static-libgcc -static-libstdc++" pip install tweedledum --no-binary :all:
+```
+
+Note that such command requires a working `gcc10` installation. (It also works
+with `gcc11`, but no further tests were made.) I recommend the use of 
+[Homebrew](https://brew.sh) to install `gcc`. (Or maybe 
+[Tigerbrew](https://github.com/mistydemeo/tigerbrew))
+
 ## License
 
 This software is licensed under the MIT licence (see