diff --git a/ci.sh b/ci.sh
index 3aa27b5..2dca184 100755
--- a/ci.sh
+++ b/ci.sh
@@ -34,26 +34,43 @@ set +x
 gend
 }
 
-# Build yosys (from scratch)
-# Not used: too long.
+# Build yosys (from scratch) using CMake.
+# ABI guarantee: plugin and yosys are compiled with the same toolchain and
+# headers, so std::source_location symbol names will always match.
 do_yosys_build ()
 {
 gstart "[Build] yosys" "$ANSI_MAGENTA"
 
+set -x
+
+# CMake 3.28+ is required.  Ubuntu 22.04 apt ships 3.22, so get a recent
+# version via pip.  --break-system-packages not needed on 22.04.
 sudo apt-get install -y --no-install-recommends \
      build-essential clang bison flex \
-     libreadline-dev gawk tcl-dev libffi-dev git \
-     graphviz xdot pkg-config python3 libboost-system-dev \
-     libboost-python-dev libboost-filesystem-dev zlib1g-dev
-
-git clone https://github.com/YosysHQ/yosys.git
-cd yosys
-git submodule update --init
-make config-clang
-make -j4
-sudo make install
-cd ..
+     libreadline-dev tcl-dev libffi-dev git \
+     pkg-config python3 python3-pip zlib1g-dev
+pip3 install --quiet --upgrade cmake
+export PATH="$HOME/.local/bin:$PATH"
+
+cmake --version
+
+git clone --recursive https://github.com/YosysHQ/yosys.git
+cmake \
+    -S yosys \
+    -B yosys/build \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_INSTALL_PREFIX=/usr/local \
+    -DYOSYS_INSTALL_DRIVER=ON \
+    -DYOSYS_INSTALL_LIBRARY=ON \
+    -DYOSYS_WITH_PYTHON=OFF \
+    -DBUILD_SHARED_LIBS=ON
+cmake --build yosys/build -j$(nproc)
+sudo cmake --install yosys/build
+
+which yosys
+yosys --version
 
+set +x
 gend
 }
 
@@ -116,12 +133,8 @@ yosys --version
 clang++ --version
 
 make
-#cp ghdl.so /tmp/ghdl_yosys.so
-
-ldd -v ghdl.so
 
 gend
-
 }
 
 # Run the testsuite