diff --git a/indra/cmake/00-Common.cmake b/indra/cmake/00-Common.cmake
index bb78347958..5d1572e915 100755
--- a/indra/cmake/00-Common.cmake
+++ b/indra/cmake/00-Common.cmake
@@ -254,6 +254,16 @@ if (DARWIN)
   # NOTE: it's critical to have both CXX_FLAGS and C_FLAGS covered.
   set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O0 ${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
   set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O0 ${CMAKE_C_FLAGS_RELWITHDEBINFO}")
+  if (USE_AVX_OPTIMIZATION)
+    if (XCODE_VERSION GREATER 4.9)
+      set(CMAKE_XCODE_ATTRIBUTE_CLANG_X86_VECTOR_INSTRUCTIONS AVX)
+      set(CMAKE_XCODE_ATTRIBUTE_GCC_OPTIMIZATION_LEVEL -Ofast)
+      set(CMAKE_CXX_FLAGS_RELEASE "-Ofast -mavx ${CMAKE_CXX_FLAGS_RELEASE}")
+      set(CMAKE_C_FLAGS_RELEASE "-Ofast -mavx ${CMAKE_C_FLAGS_RELEASE}")
+	else (XCODE_VERSION GREATER 4.9)
+	  error("Darwin AVX Optimizations only available on Xcode5 with Clang, silly person!")
+	endif (XCODE_VERSION GREATER 4.9)
+  endif (USE_AVX_OPTIMIZATION)
   if (XCODE_VERSION GREATER 4.2)
     set(ENABLE_SIGNING TRUE)
     set(SIGNING_IDENTITY "Developer ID Application: Linden Research, Inc.")