diff --git a/indra/cmake/Variables.cmake b/indra/cmake/Variables.cmake
index 0bcb3a38b003847893ccccd12ec82c6bc782e1c9..28315e66e072cdfbd3f14fa47acacd6b5cc934df 100644
--- a/indra/cmake/Variables.cmake
+++ b/indra/cmake/Variables.cmake
@@ -48,9 +48,9 @@ if (EXISTS ${CMAKE_SOURCE_DIR}/Server.cmake)
   # We use this as a marker that you can try to use the proprietary libraries.
   set(INSTALL_PROPRIETARY ON CACHE BOOL "Install proprietary binaries")
 endif (EXISTS ${CMAKE_SOURCE_DIR}/Server.cmake)
-if (INSTALL_PROPRIETARY)
+if (LINUX AND INSTALL_PROPRIETARY)
   set(BUILD_HEADLESS ON CACHE BOOL "Build headless libraries.")
-endif (INSTALL_PROPRIETARY)
+endif (LINUX AND INSTALL_PROPRIETARY)
 set(TEMPLATE_VERIFIER_OPTIONS "" CACHE STRING "Options for scripts/template_verifier.py")
 set(TEMPLATE_VERIFIER_MASTER_URL "http://bitbucket.org/lindenlab/master-message-template/raw/tip/message_template.msg" CACHE STRING "Location of the master message template")