diff --git a/extension/llm/custom_ops/CMakeLists.txt b/extension/llm/custom_ops/CMakeLists.txt
index 8a43a5ddf5c..a0ba0a2eb42 100644
--- a/extension/llm/custom_ops/CMakeLists.txt
+++ b/extension/llm/custom_ops/CMakeLists.txt
@@ -130,6 +130,8 @@ if(EXECUTORCH_BUILD_KERNELS_LLM_AOT)
     ${CMAKE_CURRENT_SOURCE_DIR}/op_tile_crop.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/op_tile_crop_aot.cpp
   )
+  # This lib compiles real PyTorch headers, which require C++20.
+  set_target_properties(custom_ops_aot_lib PROPERTIES CXX_STANDARD 20)
   target_include_directories(
     custom_ops_aot_lib PRIVATE "${_common_include_directories}"
   )
diff --git a/tools/cmake/Codegen.cmake b/tools/cmake/Codegen.cmake
index 4253fa44dc5..05d1af9725a 100644
--- a/tools/cmake/Codegen.cmake
+++ b/tools/cmake/Codegen.cmake
@@ -254,6 +254,8 @@ function(gen_custom_ops_aot_lib)
   find_package_torch()
   # This lib uses ATen lib, so we explicitly enable rtti and exceptions.
   target_compile_options(${GEN_LIB_NAME} PRIVATE -frtti -fexceptions)
+  # ATen headers require C++20.
+  set_target_properties(${GEN_LIB_NAME} PROPERTIES CXX_STANDARD 20)
   target_compile_definitions(${GEN_LIB_NAME} PRIVATE USE_ATEN_LIB=1)
   include_directories(${TORCH_INCLUDE_DIRS})
   target_link_libraries(${GEN_LIB_NAME} PRIVATE torch)