diff --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -125,7 +125,7 @@
     # binaries.
     if ("${os}" STREQUAL "osx")
       find_darwin_sdk_version(macosx_sdk_version "macosx")
-      if ("${macosx_sdk_version}" VERSION_GREATER 10.15 OR "${macosx_sdk_version}" VERSION_EQUAL 10.15)
+      if ("${macosx_sdk_version}" VERSION_GREATER_EQUAL 10.15)
         message(STATUS "Disabling i386 slice for ${valid_archs}")
         list(REMOVE_ITEM archs "i386")
       endif()
diff --git a/compiler-rt/lib/tsan/CMakeLists.txt b/compiler-rt/lib/tsan/CMakeLists.txt
--- a/compiler-rt/lib/tsan/CMakeLists.txt
+++ b/compiler-rt/lib/tsan/CMakeLists.txt
@@ -114,6 +114,11 @@
 add_compiler_rt_component(tsan)
 
 if(APPLE)
+  find_darwin_sdk_version(macosx_sdk_version "macosx")
+  if ("${macosx_sdk_version}" VERSION_LESS 10.12)
+    message(FATAL_ERROR "Building the TSan runtime requires at least macOS SDK 10.12")
+  endif()
+
   add_asm_sources(TSAN_ASM_SOURCES rtl/tsan_rtl_amd64.S rtl/tsan_rtl_aarch64.S)
 
   set(TSAN_LINK_LIBS ${SANITIZER_COMMON_LINK_LIBS})