diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -134,6 +134,8 @@
     set(RUNTIMES_${target}_LLVM_ENABLE_ASSERTIONS OFF CACHE BOOL "")
     set(RUNTIMES_${target}_SANITIZER_CXX_ABI "libc++" CACHE STRING "")
     set(RUNTIMES_${target}_SANITIZER_CXX_ABI_INTREE ON CACHE BOOL "")
+    set(RUNTIMES_${target}_SANITIZER_TEST_CXX "libc++" CACHE STRING "")
+    set(RUNTIMES_${target}_SANITIZER_TEST_CXX_INTREE ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_TEST_COMPILER_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")
     set(RUNTIMES_${target}_SANITIZER_COMMON_TEST_TARGET_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")
     set(RUNTIMES_${target}_TSAN_TEST_TARGET_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")