diff --git a/.github/workflows/wheels.yml b/.github/workflows/wheels.yml
index 5961f364a..c6af2c8b2 100644
--- a/.github/workflows/wheels.yml
+++ b/.github/workflows/wheels.yml
@@ -91,7 +91,7 @@ jobs:
           # manylinux2014 (default) does not have a modern enough C++ compiler for Yosys
           CIBW_MANYLINUX_X86_64_IMAGE: manylinux_2_28
           CIBW_MANYLINUX_AARCH64_IMAGE: manylinux_2_28
-          CIBW_BEFORE_ALL: bash ./.github/workflows/cibw_before_all.sh
+          CIBW_BEFORE_ALL: bash ./.github/workflows/wheels/cibw_before_all.sh
           CIBW_ENVIRONMENT: >
             CXXFLAGS=-I./boost/pfx/include
             LINKFLAGS=-L./boost/pfx/lib
@@ -103,7 +103,8 @@ jobs:
             PKG_CONFIG_PATH=./ffi/pfx/lib/pkgconfig
             MACOSX_DEPLOYMENT_TARGET=11
             makeFlags='BOOST_PYTHON_LIB=./boost/pfx/lib/libboost_python*.a CONFIG=clang'
-          CIBW_BEFORE_BUILD: bash ./.github/workflows/cibw_before_build.sh
+          CIBW_BEFORE_BUILD: bash ./.github/workflows/wheels/cibw_before_build.sh
+          CIBW_TEST_COMMAND: python3 -c "from pyosys import libyosys as ys;d=ys.Design();ys.run_pass('help', d)"
       - uses: actions/upload-artifact@v3
         with:
           path: ./dist/*.whl
diff --git a/.github/workflows/_run_cibw_linux.py b/.github/workflows/wheels/_run_cibw_linux.py
similarity index 94%
rename from .github/workflows/_run_cibw_linux.py
rename to .github/workflows/wheels/_run_cibw_linux.py
index 675817ae0..894470a5a 100644
--- a/.github/workflows/_run_cibw_linux.py
+++ b/.github/workflows/wheels/_run_cibw_linux.py
@@ -24,7 +24,7 @@ import subprocess
 __dir__ = os.path.dirname(os.path.abspath(__file__))
 
 
-workflow = yaml.safe_load(open(os.path.join(__dir__, "wheels.yml")))
+workflow = yaml.safe_load(open(os.path.join(os.path.dirname(__dir__), "wheels.yml")))
 
 env = os.environ.copy()
 
diff --git a/.github/workflows/cibw_before_all.sh b/.github/workflows/wheels/cibw_before_all.sh
similarity index 55%
rename from .github/workflows/cibw_before_all.sh
rename to .github/workflows/wheels/cibw_before_all.sh
index 934902380..28aae85ac 100644
--- a/.github/workflows/cibw_before_all.sh
+++ b/.github/workflows/wheels/cibw_before_all.sh
@@ -11,11 +11,13 @@ if command -v apk &> /dev/null; then
     apk add flex bison
 fi
 
-## macOS/Windows -- install in GitHub Action itself, not container
+## macOS/Windows -- installed in GitHub Action itself, not container
 
 # Build Static FFI (platform-dependent but not Python version dependent)
 cd ffi
-SHELL=bash CFLAGS=-fPIC CXXFLAGS=-fPIC ./configure --prefix=$PWD/pfx
-
-make install -j$(getconf _NPROCESSORS_ONLN 2>/dev/null || sysctl -n hw.ncpu)
+## Ultimate libyosys.so will be shared, so we need fPIC for the static libraries
+CFLAGS=-fPIC CXXFLAGS=-fPIC ./configure --prefix=$PWD/pfx
+## Without this, SHELL has a space in its path which breaks the makefile
+make install -j$(getconf _NPROCESSORS_ONLN 2>/dev/null || sysctl -n hw.ncpu) SHELL=bash
+## Forces static library to be used in all situations
 sed -i.bak 's@-L${toolexeclibdir} -lffi@${toolexeclibdir}/libffi.a@' ./pfx/lib/pkgconfig/libffi.pc
diff --git a/.github/workflows/cibw_before_build.sh b/.github/workflows/wheels/cibw_before_build.sh
similarity index 80%
rename from .github/workflows/cibw_before_build.sh
rename to .github/workflows/wheels/cibw_before_build.sh
index 03baf110b..29fffe090 100644
--- a/.github/workflows/cibw_before_build.sh
+++ b/.github/workflows/wheels/cibw_before_build.sh
@@ -1,6 +1,13 @@
 set -e
 set -x
 
+# Don't use objects from previous compiles on Windows/macOS
+make clean
+
+# DEBUG: show python3 and python3-config outputs
+python3 --version
+python3-config --includes
+
 # Build boost
 cd ./boost
 ## Delete the artefacts from previous builds (if any)