diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
index e507724edb3e..70891bbec613 100644
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -66,8 +66,10 @@ if (NOT COMPILER_RT_STANDALONE_BUILD)
   # Windows where we need to use clang-cl instead.
   if(NOT MSVC)
     set(COMPILER_RT_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)
+    set(COMPILER_RT_TEST_CXX_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++)
   else()
     set(COMPILER_RT_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang.exe)
+    set(COMPILER_RT_TEST_CXX_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++.exe)
   endif()
 else()
   # Take output dir and install path from the user.
@@ -81,6 +83,7 @@ else()
   option(COMPILER_RT_ENABLE_WERROR "Fail and stop if warning is triggered" OFF)
   # Use a host compiler to compile/link tests.
   set(COMPILER_RT_TEST_COMPILER ${CMAKE_C_COMPILER} CACHE PATH "Compiler to use for testing")
+  set(COMPILER_RT_TEST_CXX_COMPILER ${CMAKE_CXX_COMPILER} CACHE PATH "C++ Compiler to use for testing")
 
   if (NOT LLVM_CONFIG_PATH)
     find_program(LLVM_CONFIG_PATH "llvm-config"
diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
index 660488dd26ab..c55f9e4a1491 100644
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
@@ -293,11 +293,12 @@ macro(add_custom_libcxx name prefix)
     SOURCE_DIR ${COMPILER_RT_LIBCXX_PATH}
     CMAKE_ARGS -DCMAKE_MAKE_PROGRAM:STRING=${CMAKE_MAKE_PROGRAM}
                -DCMAKE_C_COMPILER=${COMPILER_RT_TEST_COMPILER}
-               -DCMAKE_CXX_COMPILER=${COMPILER_RT_TEST_COMPILER}
+               -DCMAKE_CXX_COMPILER=${COMPILER_RT_TEST_CXX_COMPILER}
                -DCMAKE_C_FLAGS=${LIBCXX_CFLAGS}
                -DCMAKE_CXX_FLAGS=${LIBCXX_CFLAGS}
                -DCMAKE_BUILD_TYPE=Release
                -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
+               -DLLVM_PATH=${LLVM_MAIN_SRC_DIR}
     LOG_BUILD 1
     LOG_CONFIGURE 1
     LOG_INSTALL 1