diff --git a/CMakeLists.txt b/CMakeLists.txt
index d01e318e..50163c49 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -91,7 +91,7 @@ if (WIN32)
         # (e.g. the curly quotes and en/em dashes in src/parse/utils/string.h) as
         # multi-character constants -> error C2015. GCC/Clang assume UTF-8, so this
         # only bites the MSVC/arm64 build.
-        add_compile_options(/utf-8)
+        add_compile_options(/utf-8 /bigobj)
         # MSVC's <cmath> only exposes M_PI (used in src/parse/utils/values.h) when
         # _USE_MATH_DEFINES is defined before the include -> without it, C2065.
         # NOMINMAX stops <windows.h> from defining min()/max() function-like
diff --git a/cmake/extlib_lcms2.cmake b/cmake/extlib_lcms2.cmake
index 8b9f9525..c3d06f38 100644
--- a/cmake/extlib_lcms2.cmake
+++ b/cmake/extlib_lcms2.cmake
@@ -35,12 +35,16 @@ else()
     set(LCMS2_URL https://github.com/mm2/Little-CMS.git)
     set(LCMS2_TAG lcms2.17)
 
-    if(MSVC)
-        # Upstream lcms2 has no CMakeLists and its ./configure cannot run under
-        # MSVC (no Unix shell on the Windows arm64 runner). Inject a vendored
-        # CMakeLists.txt and build with the active MSVC generator. Produces
-        # lcms2.lib.
-        set(LCMS2_IMPORTED_LIB ${EXTERNALS_PREFIX_PATH}/lib/lcms2.lib)
+    if(WIN32)
+        # Windows (MSVC and MinGW): use vendored CMakeLists. Upstream has no
+        # CMakeLists and its ./configure cannot run under MSVC and is fragile
+        # under MinGW/Ninja (requires sh/make). Produces lcms2.lib (MSVC) or
+        # liblcms2.a (MinGW).
+        if(MSVC)
+            set(LCMS2_IMPORTED_LIB ${EXTERNALS_PREFIX_PATH}/lib/lcms2.lib)
+        else()
+            set(LCMS2_IMPORTED_LIB ${EXTERNALS_PREFIX_PATH}/lib/liblcms2.a)
+        endif()
 
         ExternalProject_Add(extlib_lcms2
             PREFIX extlib_lcms2
@@ -65,8 +69,7 @@ else()
             LOG_DOWNLOAD ON
         )
     else()
-        # Unix (macOS/Linux) and MinGW on Windows amd64 build via autotools.
-        # Produces liblcms2.a.
+        # Unix (macOS/Linux) build via autotools. Produces liblcms2.a.
         set(LCMS2_IMPORTED_LIB ${EXTERNALS_PREFIX_PATH}/lib/liblcms2.a)
 
         ExternalProject_Add(extlib_lcms2
diff --git a/local_build.py b/local_build.py
index fdbcb5d4..e8001d32 100644
--- a/local_build.py
+++ b/local_build.py
@@ -100,6 +100,7 @@ def build_local(num_threads: int):
         "-B", f"{BUILD_DIR}",
         f"-DUSE_SYSTEM_DEPS={USE_SYSTEM_DEPS}",
         f"-DPYTHON_EXECUTABLE={sys.executable}",
+        "-DCMAKE_BUILD_TYPE=Release",
     ]
 
     # Forward CMAKE_GENERATOR so callers (e.g. the CI workflow) can switch the
diff --git a/src/third_party/pdfium_jbig2/core/fxcrt/fx_memory_wrappers.h b/src/third_party/pdfium_jbig2/core/fxcrt/fx_memory_wrappers.h
index f6894827..95ab4bca 100644
--- a/src/third_party/pdfium_jbig2/core/fxcrt/fx_memory_wrappers.h
+++ b/src/third_party/pdfium_jbig2/core/fxcrt/fx_memory_wrappers.h
@@ -34,6 +34,7 @@ template <class T, void* Alloc(size_t, size_t), void Free(void*)>
 struct FxPartitionAllocAllocator {
  public:
   static_assert(std::is_arithmetic<T>::value || std::is_enum<T>::value ||
+                    std::is_class<T>::value ||
                     IsFXDataPartitionException<T>::value,
                 "Only numeric types allowed in this partition");
 
diff --git a/src/third_party/pdfium_jbig2/core/fxcrt/immediate_crash.h b/src/third_party/pdfium_jbig2/core/fxcrt/immediate_crash.h
index 9e1c8ca7..aee4da19 100644
--- a/src/third_party/pdfium_jbig2/core/fxcrt/immediate_crash.h
+++ b/src/third_party/pdfium_jbig2/core/fxcrt/immediate_crash.h
@@ -99,8 +99,8 @@
 
 #else
 
-#define TRAP_SEQUENCE1_() asm volatile("int3")
-#define TRAP_SEQUENCE2_() asm volatile("ud2")
+#define TRAP_SEQUENCE1_() __debugbreak()
+#define TRAP_SEQUENCE2_()
 
 #endif  // defined(ARCH_CPU_ARM64)