diff --git a/deps/python3/arm64-unicodectype.props b/deps/python3/arm64-unicodectype.props
new file mode 100644
index 0000000000..5f5727c842
--- /dev/null
+++ b/deps/python3/arm64-unicodectype.props
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Compiles Objects/unicodectype.c without optimisation. VS 2026's ARM64 code
+     generator needs about 27 GB for _PyUnicode_ToNumeric, a switch with 1951
+     cases. CPython has the same workaround (python/cpython#153668). -->
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <ClCompile Update="..\Objects\unicodectype.c">
+      <Optimization>Disabled</Optimization>
+      <WholeProgramOptimization>false</WholeProgramOptimization>
+    </ClCompile>
+  </ItemGroup>
+</Project>
diff --git a/deps/python3/python3.cmake b/deps/python3/python3.cmake
index 2eae315d0b..3e063fac4e 100644
--- a/deps/python3/python3.cmake
+++ b/deps/python3/python3.cmake
@@ -88,8 +88,18 @@ if(WIN32)
         list(APPEND _python_env_args "PreferredToolArchitecture=${_python_tool_arch}")
     endif()
 
+    # MSBuild reads extra switches from PCbuild/msbuild.rsp.
+    set(_python_rsp "/p:PlatformToolset=${_python_platform_toolset}\n")
+    # VS 2026's ARM64 code generator needs about 27 GB for one function in
+    # Objects/unicodectype.c (python/cpython#153668); the property sheet compiles
+    # that file without optimisation.
+    if(_python_pcbuild_platform STREQUAL "ARM64")
+        file(TO_NATIVE_PATH "${CMAKE_CURRENT_LIST_DIR}/arm64-unicodectype.props" _python_arm64_props)
+        string(APPEND _python_rsp "/p:ForceImportAfterCppTargets=\"${_python_arm64_props}\"\n")
+    endif()
+    file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/python3-msbuild.rsp" "${_python_rsp}")
     set(_conf_cmd
-        cmd /c "echo /p:PlatformToolset=${_python_platform_toolset}>PCbuild\\msbuild.rsp"
+        ${CMAKE_COMMAND} -E copy "${CMAKE_CURRENT_BINARY_DIR}/python3-msbuild.rsp" <SOURCE_DIR>/PCbuild/msbuild.rsp
     )
     set(_build_cmd
         ${CMAKE_COMMAND} -E env ${_python_env_args}