diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 842b3b20..1852c8a9 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -107,14 +107,15 @@ jobs:
       - uses: actions/checkout@v6.0.2
 
       - name: Install packages
-        run: sudo apt-get -y install build-essential cmake
+        run: sudo apt-get -y install build-essential cmake ninja-build
 
       - name: Configure
         run: |
           cmake -B build \
+            -G Ninja \
             -DCMAKE_BUILD_TYPE=Release \
-            -DLCMS2_FAST_FLOAT=ON \
-            -DLCMS2_THREADED=ON \
+            -DLCMS2_WITH_FASTFLOAT=ON \
+            -DLCMS2_WITH_THREADS=ON \
             -DLCMS2_BUILD_TESTS=ON
 
       - name: Build
@@ -134,9 +135,10 @@ jobs:
       - name: Configure
         run: |
           cmake -B build \
+            -G Ninja \
             -DCMAKE_BUILD_TYPE=Release \
-            -DLCMS2_FAST_FLOAT=ON \
-            -DLCMS2_THREADED=ON \
+            -DLCMS2_WITH_FASTFLOAT=ON \
+            -DLCMS2_WITH_THREADS=ON \
             -DLCMS2_BUILD_TESTS=ON
 
       - name: Build
@@ -164,8 +166,8 @@ jobs:
       - name: Configure
         run: |
           cmake -B build -A ${{ matrix.arch }} `
-            -DLCMS2_FAST_FLOAT=ON `
-            -DLCMS2_THREADED=ON `
+            -DLCMS2_WITH_FASTFLOAT=ON `
+            -DLCMS2_WITH_THREADS=ON `
             -DLCMS2_BUILD_TESTS=ON
 
       - name: Build
@@ -174,3 +176,65 @@ jobs:
       - name: Run tests
         run: ctest --test-dir build -C Release --output-on-failure
 
+  MSYS2-cmake:
+    strategy:
+      matrix:
+        sys: [ MINGW64, UCRT64 ]
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    steps:
+      - uses: actions/checkout@v6.0.2
+
+      - uses: msys2/setup-msys2@v2
+        with:
+          msystem: ${{ matrix.sys }}
+          update: true
+          pacboy: cmake:p gcc:p ninja:p
+
+      - name: Configure
+        run: |
+          cmake -B build \
+            -G Ninja \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DLCMS2_WITH_FASTFLOAT=ON \
+            -DLCMS2_WITH_THREADS=ON \
+            -DLCMS2_BUILD_TESTS=ON
+
+      - name: Build
+        run: cmake --build build --parallel
+
+      - name: Run tests
+        run: ctest --test-dir build --output-on-failure
+
+  Cygwin-cmake:
+    runs-on: windows-latest
+    env:
+      CHERE_INVOKING: "1"
+    defaults:
+      run:
+        shell: C:\cygwin64\bin\bash.exe --login -eo pipefail -o igncr '{0}'
+    steps:
+      - uses: actions/checkout@v6.0.2
+
+      - uses: cygwin/cygwin-install-action@v6
+        with:
+          install-dir: 'C:\cygwin64'
+          packages: cmake ninja gcc-core gcc-g++
+
+      - name: Configure
+        run: |
+          cmake -B build \
+            -G Ninja \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DLCMS2_WITH_FASTFLOAT=ON \
+            -DLCMS2_WITH_THREADS=ON \
+            -DLCMS2_BUILD_TESTS=ON
+
+      - name: Build
+        run: cmake --build build --parallel
+
+      - name: Run tests
+        run: ctest --test-dir build --output-on-failure
+
diff --git a/cmake/Lcms2Plugins.cmake b/cmake/Lcms2Plugins.cmake
index 93a8a8bd..b3054bc0 100644
--- a/cmake/Lcms2Plugins.cmake
+++ b/cmake/Lcms2Plugins.cmake
@@ -65,6 +65,9 @@ function(lcms2_add_plugins)
         "${PROJECT_SOURCE_DIR}/plugins/fast_float/include"
         "${PROJECT_SOURCE_DIR}/plugins/fast_float/src/../include"
     )
+    if(LCMS2_DEFINE_CMS_DONT_USE_SSE2)
+      target_compile_definitions(lcms2_fast_float PRIVATE CMS_DONT_USE_SSE2=1)
+    endif()
   endif()
 
   if(LCMS2_WITH_THREADED_PLUGIN)
diff --git a/plugins/fast_float/src/fast_8_curves.c b/plugins/fast_float/src/fast_8_curves.c
index 145d95ca..b5e94ad1 100644
--- a/plugins/fast_float/src/fast_8_curves.c
+++ b/plugins/fast_float/src/fast_8_curves.c
@@ -408,7 +408,7 @@ cmsBool Optimize8ByJoiningCurves(_cmsTransform2Fn* TransformFn,
     *dwFlags |= cmsFLAGS_NOCACHE;
     *dwFlags &= ~cmsFLAGS_CAN_CHANGE_FORMATTER;
     *UserData = Data;
-    *FreeUserData = _cmsFree;
+    *FreeUserData = _fast_float_free_user_data;
 
     // Maybe the curves are linear at the end
     if (nChans == 1)
diff --git a/plugins/fast_float/src/fast_float_cmyk.c b/plugins/fast_float/src/fast_float_cmyk.c
index 125d4798..f6597017 100644
--- a/plugins/fast_float/src/fast_float_cmyk.c
+++ b/plugins/fast_float/src/fast_float_cmyk.c
@@ -380,7 +380,7 @@ cmsBool OptimizeCLUTCMYKTransform(_cmsTransform2Fn* TransformFn,
     *Lut = OptimizedLUT;
     *TransformFn = FloatCMYKCLUTEval;
     *UserData   = pcmyk;
-    *FreeDataFn = _cmsFree;
+    *FreeDataFn = _fast_float_free_user_data;
     *dwFlags &= ~cmsFLAGS_CAN_CHANGE_FORMATTER;
     return TRUE;
 
diff --git a/plugins/fast_float/src/fast_float_internal.h b/plugins/fast_float/src/fast_float_internal.h
index 01114a12..2dc07780 100644
--- a/plugins/fast_float/src/fast_float_internal.h
+++ b/plugins/fast_float/src/fast_float_internal.h
@@ -273,5 +273,10 @@ cmsBool OptimizeCLUTLabTransform(_cmsTransform2Fn* TransformFn,
                                  cmsUInt32Number* OutputFormat, 
                                  cmsUInt32Number* dwFlags);      
 
+// Wrapper for _cmsFree that matches the _cmsFreeUserDataFn calling convention.
+// On Win32, _cmsFree uses __stdcall (CMSEXPORT) but _cmsFreeUserDataFn is __cdecl.
+// Using _cmsFree directly as a _cmsFreeUserDataFn would cause a calling convention
+// mismatch on 32-bit Windows builds. This wrapper uses the default (cdecl) convention.
+cmsINLINE void _fast_float_free_user_data(cmsContext ContextID, void* Data) { _cmsFree(ContextID, Data); }
 
 #endif
diff --git a/plugins/fast_float/src/fast_float_sup.c b/plugins/fast_float/src/fast_float_sup.c
index ba523f24..d491354b 100644
--- a/plugins/fast_float/src/fast_float_sup.c
+++ b/plugins/fast_float/src/fast_float_sup.c
@@ -83,11 +83,20 @@ cmsBool Floating_Point_Transforms_Dispatcher(_cmsTransform2Fn* TransformFn,
     return FALSE;
 }
 
+// On Win32, CMSEXPORT expands to __stdcall but cmsFormatterFactory is __cdecl.
+// This wrapper has the cdecl calling convention so it can be stored in the plugin struct.
+static cmsFormatter Formatter_15Bit_Factory_wrapper(cmsUInt32Number Type,
+                                                    cmsFormatterDirection Dir,
+                                                    cmsUInt32Number dwFlags)
+{
+    return Formatter_15Bit_Factory(Type, Dir, dwFlags);
+}
+
 // The Plug-in entry points
 static cmsPluginFormatters PluginFastFloat = {
               { cmsPluginMagicNumber, REQUIRED_LCMS_VERSION, cmsPluginFormattersSig, NULL },
 
-              Formatter_15Bit_Factory
+              Formatter_15Bit_Factory_wrapper
 };
 
 static cmsPluginTransform PluginList = {
diff --git a/plugins/fast_float/src/fast_float_tethra.c b/plugins/fast_float/src/fast_float_tethra.c
index 7eaa4e77..a0378cea 100644
--- a/plugins/fast_float/src/fast_float_tethra.c
+++ b/plugins/fast_float/src/fast_float_tethra.c
@@ -349,7 +349,7 @@ cmsBool OptimizeCLUTRGBTransform(_cmsTransform2Fn* TransformFn,
     *Lut = OptimizedLUT;
     *TransformFn = FloatCLUTEval;
     *UserData   = pfloat;
-    *FreeDataFn = _cmsFree;
+    *FreeDataFn = _fast_float_free_user_data;
     *dwFlags &= ~cmsFLAGS_CAN_CHANGE_FORMATTER;
     return TRUE;