diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -57,6 +57,9 @@
 
 include_directories("${LIBCXXABI_LIBCXX_INCLUDES}")
 
+# stdlib_stdexcept.cpp depends on libc++ internals.
+include_directories("${LIBCXXABI_LIBCXX_PATH}")
+
 if (LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL)
   add_definitions(-DHAVE___CXA_THREAD_ATEXIT_IMPL)
 endif()
diff --git a/libcxxabi/src/stdlib_stdexcept.cpp b/libcxxabi/src/stdlib_stdexcept.cpp
--- a/libcxxabi/src/stdlib_stdexcept.cpp
+++ b/libcxxabi/src/stdlib_stdexcept.cpp
@@ -6,7 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "../../libcxx/src/include/refstring.h"
 #include "stdexcept"
 #include "new"
 #include <cstdlib>
@@ -14,6 +13,9 @@
 #include <cstdint>
 #include <cstddef>
 
+// This includes an implementation file from libc++.
+#include "src/include/refstring.h"
+
 static_assert(sizeof(std::__libcpp_refstring) == sizeof(const char *), "");
 
 namespace std  // purposefully not using versioning namespace
diff --git a/llvm/utils/gn/secondary/libcxxabi/src/BUILD.gn b/llvm/utils/gn/secondary/libcxxabi/src/BUILD.gn
--- a/llvm/utils/gn/secondary/libcxxabi/src/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxxabi/src/BUILD.gn
@@ -62,6 +62,9 @@
   include_dirs = [
     "//libcxxabi/include",
     "//libcxx/include",
+
+    # stdlib_stdexcept.cpp depends on libc++ internals.
+    "//libcxx",
   ]
   cflags_cc = [ "-nostdinc++" ]
   defines = [ "_LIBCXXABI_BUILDING_LIBRARY" ]