diff --git a/lib/execjs/pcruntime.rb b/lib/execjs/pcruntime.rb
index fcf44d5..d01f10d 100644
--- a/lib/execjs/pcruntime.rb
+++ b/lib/execjs/pcruntime.rb
@@ -4,4 +4,4 @@
 require 'execjs/pcruntime/version'
 require 'execjs/pcruntime/runtimes'
 
-ExecJS.runtime = ExecJS::Runtimes.autodetect
+ExecJS.runtime = ExecJS::Runtimes.from_environment || ExecJS::Runtimes::PCRuntime