diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index f777b9c1c14..a1a16b99eb1 100644
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -8,6 +8,7 @@ include(CheckIncludeFileCXX)
 include(CheckLibraryExists)
 include(CheckSymbolExists)
 include(CheckFunctionExists)
+include(CheckCCompilerFlag)
 include(CheckCXXSourceCompiles)
 include(TestBigEndian)
 
@@ -179,6 +180,14 @@ check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
 find_package(Backtrace)
 set(HAVE_BACKTRACE ${Backtrace_FOUND})
 set(BACKTRACE_HEADER ${Backtrace_HEADER})
+
+# Prevent check_symbol_exists from using API that is not supported for a given
+# deployment target.
+check_c_compiler_flag("-Werror=unguarded-availability-new" "C_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW")
+if(C_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror=unguarded-availability-new")
+endif()
+
 check_symbol_exists(_Unwind_Backtrace "unwind.h" HAVE__UNWIND_BACKTRACE)
 check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)
 check_symbol_exists(sysconf unistd.h HAVE_SYSCONF)
diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index 04596a6ff63..a2ab1283808 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -383,6 +383,7 @@ elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
   append_if(LLVM_ENABLE_WERROR "-Werror" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   append_if(LLVM_ENABLE_WERROR "-Wno-error" CMAKE_REQUIRED_FLAGS)
   add_flag_if_supported("-Werror=date-time" WERROR_DATE_TIME)
+  add_flag_if_supported("-Werror=unguarded-availability-new" WERROR_UNGUARDED_AVAILABILITY_NEW)
   if (LLVM_ENABLE_CXX1Y)
     check_cxx_compiler_flag("-std=c++1y" CXX_SUPPORTS_CXX1Y)
     append_if(CXX_SUPPORTS_CXX1Y "-std=c++1y" CMAKE_CXX_FLAGS)