diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -40,4 +40,8 @@
 
 API Changes
 -----------
-- ...
+- By default, libc++abi will not include the definition for new and delete,
+  since those are provided in libc++. Vendors wishing to provide new and
+  delete in libc++abi can build the library with ``-DLIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS=ON``
+  to get back the old behavior.
+
diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -62,12 +62,9 @@
   "Build libc++abi with an externalized threading library.
    This option may only be set to ON when LIBCXXABI_ENABLE_THREADS=ON" OFF)
 
-# FIXME: This option should default to off. Unfortunatly GCC 4.9 fails to link
-# programs to due undefined references to new/delete in libc++abi. Once this
-# has been fixed or worked around the default value should be changed.
 option(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS
     "Build libc++abi with definitions for operator new/delete. Normally libc++
-    provides these definitions" ON)
+    provides these definitions" OFF)
 option(LIBCXXABI_BUILD_32_BITS "Build 32 bit libc++abi." ${LLVM_BUILD_32_BITS})
 option(LIBCXXABI_INCLUDE_TESTS "Generate build targets for the libc++abi unit tests." ${LLVM_INCLUDE_TESTS})
 set(LIBCXXABI_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING