diff --git a/test/helper.rb b/test/helper.rb
index eadd5c62..de82cd6b 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -8,6 +8,7 @@ require 'minitest/autorun'
 
 $TESTING = true
 # disable minitest/parallel threads
+ENV["MT_CPU"] = 0
 ENV["N"] = "0"
 # Disable any stupid backtrace cleansers
 ENV["BACKTRACE"] = "1"