diff --git a/libcxx/docs/Contributing.rst b/libcxx/docs/Contributing.rst
--- a/libcxx/docs/Contributing.rst
+++ b/libcxx/docs/Contributing.rst
@@ -70,6 +70,7 @@
 2. Update the ``libcxx/include/__libcpp_version`` file
 3. Update the version number in ``libcxx/docs/conf.py``
 4. Update ``_LIBCPPABI_VERSION`` in ``libcxxabi/include/cxxabi.h``
+5. Update ``_LIBUNWIND_VERSION`` in ``libunwind/include/__libunwind_config.h``
 
 Exporting new symbols from the library
 ======================================
diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -478,11 +478,6 @@
   add_definitions(-D_CRT_SECURE_NO_WARNINGS)
 endif()
 
-# Define LIBCXXABI_USE_LLVM_UNWINDER for conditional compilation.
-if (LIBCXXABI_USE_LLVM_UNWINDER)
-  add_definitions(-DLIBCXXABI_USE_LLVM_UNWINDER)
-endif()
-
 if (LIBCXXABI_SILENT_TERMINATE)
   add_definitions(-DLIBCXXABI_SILENT_TERMINATE)
 endif()
diff --git a/libcxxabi/src/cxa_personality.cpp b/libcxxabi/src/cxa_personality.cpp
--- a/libcxxabi/src/cxa_personality.cpp
+++ b/libcxxabi/src/cxa_personality.cpp
@@ -1015,7 +1015,7 @@
 }
 
 // ARM register names
-#if !defined(LIBCXXABI_USE_LLVM_UNWINDER)
+#if !defined(_LIBUNWIND_VERSION)
 static const uint32_t REG_UCB = 12;  // Register to save _Unwind_Control_Block
 #endif
 static const uint32_t REG_SP = 13;
@@ -1050,7 +1050,7 @@
 
     bool native_exception = __isOurExceptionClass(unwind_exception);
 
-#if !defined(LIBCXXABI_USE_LLVM_UNWINDER)
+#if !defined(_LIBUNWIND_VERSION)
     // Copy the address of _Unwind_Control_Block to r12 so that
     // _Unwind_GetLanguageSpecificData() and _Unwind_GetRegionStart() can
     // return correct address.
diff --git a/libunwind/include/__libunwind_config.h b/libunwind/include/__libunwind_config.h
--- a/libunwind/include/__libunwind_config.h
+++ b/libunwind/include/__libunwind_config.h
@@ -9,6 +9,8 @@
 #ifndef ____LIBUNWIND_CONFIG_H__
 #define ____LIBUNWIND_CONFIG_H__
 
+#define _LIBUNWIND_VERSION 15000
+
 #if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) && \
     !defined(__ARM_DWARF_EH__)
 #define _LIBUNWIND_ARM_EHABI