diff --git a/indra/cmake/00-Common.cmake b/indra/cmake/00-Common.cmake
index 86fc2dfff5d4fc06713e945e3b4356e4be106295..84d70bd7b12b064095ce46cd1267229cf21e3ca9 100644
--- a/indra/cmake/00-Common.cmake
+++ b/indra/cmake/00-Common.cmake
@@ -74,9 +74,18 @@ if (WINDOWS)
       /nologo
       /Oy-
       /Zc:wchar_t-
-      /arch:SSE2
+#      /arch:SSE2
       /fp:fast
       )
+
+  # Nicky: x64 implies SSE2
+  if( NOT LL_64BIT_BUILD )
+    add_definitions( /arch:SSE2 )
+  else()
+   # Otherwise disable 4267 ('var' : conversion from 'size_t' to 'type', possible loss of data) 
+   # This warning alas is all over the place and fixing it will touch a lot of code.
+   add_definitions("/wd4267 /DLL_64BIT_BUILD" ) 
+  endif()
      
   # Are we using the crummy Visual Studio KDU build workaround?
   if (NOT VS_DISABLE_FATAL_WARNINGS)