diff --git a/Rakefile b/Rakefile
index 697d3e9ea..5fcad4e54 100644
--- a/Rakefile
+++ b/Rakefile
@@ -15,7 +15,7 @@ MRUBY_ROOT = ENV['MRUBY_ROOT'] || File.expand_path(File.dirname(__FILE__))
 ENABLE_GEMS = ENV['ENABLE_GEMS'] == 'true'
 
 # the default file which contains the active GEMs
-ACTIVE_GEMS = File.join(File.dirname(__FILE__), 'mrbgems', 'GEMS.active')
+ACTIVE_GEMS = ENV['ACTIVE_GEMS'] || File.expand_path('../mrbgems/GEMS.active', __FILE__)
 
 # default compile option
 COMPILE_MODE = ENV['COMPILE_MODE'] || :debug