diff --git a/build/premake/extern_libs.lua b/build/premake/extern_libs.lua
index 1fb9b28129..6e05701021 100644
--- a/build/premake/extern_libs.lua
+++ b/build/premake/extern_libs.lua
@@ -68,6 +68,7 @@ end
 --   which is unfortunately totally incompatible with our
 --   library installation rules.
 -- * depends: a table of external libraries that this library depends on
+-- * defines: a table of symbols to define
 extern_lib_defs = {
 	boost = {
 		unix_names = { "boost_signals-mt", "boost_filesystem-mt", "boost_system-mt" },
@@ -175,10 +176,25 @@ extern_lib_defs = {
 			end
 		end
 	},
-	spidermonkey = {
+	spidermonkey =
+	options["with-spidermonkey-tip"] and
+	{
+		add_func = function()
+			tinsert(package.config["Debug"  ].includepaths, libraries_dir.."spidermonkey-tip/include/debug")
+			tinsert(package.config["Testing"].includepaths, libraries_dir.."spidermonkey-tip/include/debug")
+			tinsert(package.config["Release"].includepaths, libraries_dir.."spidermonkey-tip/include/release")
+			tinsert(package.libpaths, libraries_dir.."spidermonkey-tip/lib")
+			tinsert(package.config["Debug"  ].links, "mozjs-debug")
+			tinsert(package.config["Testing"].links, "mozjs-release")
+			tinsert(package.config["Release"].links, "mozjs-release")
+		end,
+	}
+	or -- SpiderMonkey 1.6
+	{
 		win_names  = { "js32" },
 		unix_names = { "js" },
-		depends = { "nspr" }
+		depends = { "nspr" },
+		defines = { "JS_THREADSAFE" },
 	},
 	valgrind = {
 	},
@@ -274,7 +290,11 @@ local function add_extern_lib(extern_lib, def)
 	if OS ~= "windows" then
 		suffix = ""
 	end
-	
+
+	if def.defines then
+		tinsert(package.defines, def.defines)
+	end
+
 	-- OS X "Frameworks" need to be added in a special way to the link
 	-- i.e. by linkoptions += "-framework ..."
 	if OS == "macosx" and def.osx_frameworks then
diff --git a/build/premake/premake.lua b/build/premake/premake.lua
index ec2ededd4a..4dae1a0e1a 100755
--- a/build/premake/premake.lua
+++ b/build/premake/premake.lua
@@ -7,6 +7,7 @@ addoption("outpath", "Location for generated project files")
 addoption("without-tests", "Disable generation of test projects")
 addoption("without-pch", "Disable generation and usage of precompiled headers")
 addoption("with-valgrind", "Enable using valgrind for debugging functionality")
+addoption("with-spidermonkey-tip", "Use SpiderMonkey from mozilla-central tip instead of the 1.6 release")
 
 use_dcdt = false -- disable it since it's a non-Free library
 
@@ -121,6 +122,8 @@ function package_set_build_flags()
 	-- PremakeWiki says with-symbols and optimize are automatically set for
 	-- Debug and Release builds, respectively. doesn't happen though, so do it manually.
 
+	package.config["Debug"].defines = { "DEBUG" }
+
 	package.config["Testing"].buildflags = { "no-runtime-checks" }
 	package.config["Testing"].defines = { "TESTING" }
 
@@ -208,6 +211,11 @@ function package_set_build_flags()
 			end
 		end
 
+		-- To use our local SpiderMonkey library, it needs to be part of the runtime dynamic linker
+		-- path. So try to add the cwd (assuming it'll be binaries/system/) with -rpath
+		-- (TODO: is this a sane way to do it?)
+		tinsert(package.linkoptions, {"-Wl,-rpath=."})
+
 		tinsert(package.buildoptions, {
 			-- Hide symbols in dynamic shared objects by default, for efficiency and for equivalence with
 			-- Windows - they should be exported explicitly with __attribute__ ((visibility ("default")))
@@ -851,6 +859,9 @@ end
 function setup_atlas_frontend_package (package_name)
 
 	package_create(package_name, "winexe")
+	package_add_extern_libs({
+		"spidermonkey",
+	})
 
 	local source_root = "../../../source/tools/atlas/AtlasFrontends/"
 	package.files = {
diff --git a/source/scripting/SpiderMonkey.h b/source/scripting/SpiderMonkey.h
index 8b5cc16b6c..f3563dc482 100644
--- a/source/scripting/SpiderMonkey.h
+++ b/source/scripting/SpiderMonkey.h
@@ -43,8 +43,6 @@
 # define XP_UNIX
 #endif
 
-#define JS_THREADSAFE
-
 #include <js/jsapi.h>
 
 #ifndef NDEBUG