diff --git a/lib/execjs/pcruntime.rb b/lib/execjs/pcruntime.rb
index d7b8d91..fcf44d5 100644
--- a/lib/execjs/pcruntime.rb
+++ b/lib/execjs/pcruntime.rb
@@ -3,3 +3,5 @@
 require 'execjs'
 require 'execjs/pcruntime/version'
 require 'execjs/pcruntime/runtimes'
+
+ExecJS.runtime = ExecJS::Runtimes.autodetect