diff --git a/llvm/lib/Support/BLAKE3/CMakeLists.txt b/llvm/lib/Support/BLAKE3/CMakeLists.txt
index 4746c2f38f16085eb91efea025fa01f5ee9a183e..51a6ee84768db0b5103d5291b08912ed173ed04d 100644
--- a/llvm/lib/Support/BLAKE3/CMakeLists.txt
+++ b/llvm/lib/Support/BLAKE3/CMakeLists.txt
@@ -11,7 +11,7 @@ set(LLVM_BLAKE3_FILES
 # version using C intrinsics. The assembly versions are generally
 # preferred. They perform better, they perform more consistently across
 # different compilers, and they build more quickly."
-# FIXME: Figure out what is wrong with the builders when using the assembly files.
+# FIXME: Figure out what is wrong with the builders when using the assembly files and neon.
 if (FALSE)#CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64)$")
   if (MSVC)
     list(APPEND LLVM_BLAKE3_FILES
@@ -37,7 +37,7 @@ if (FALSE)#CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64)$")
   endif()
 endif()
 
-if (CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm|aarch)")
+if (FALSE)#CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm|aarch)")
   list(APPEND LLVM_BLAKE3_FILES
     BLAKE3/blake3_neon.c
   )
diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index b4ae4e89dab675ac7d4680215825239bfa03ab62..edaf5db2867e9912f3908d8d3bf7fa40bcbc53ff 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -107,7 +107,7 @@ if (MSVC)
   enable_language(ASM_MASM)
 endif()
 # FIXME: Figure out what is wrong with the builders when using the assembly files.
-add_definitions(-DBLAKE3_NO_AVX512 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_SSE41 -DBLAKE3_NO_SSE2)
+add_definitions(-DBLAKE3_NO_AVX512 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_SSE41 -DBLAKE3_NO_SSE2 -DBLAKE3_USE_NEON=0)
 
 
 add_llvm_component_library(LLVMSupport