diff --git a/lib/execjs/pcruntime.rb b/lib/execjs/pcruntime.rb
index d7b8d91..d01f10d 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.from_environment || ExecJS::Runtimes::PCRuntime
diff --git a/lib/execjs/pcruntime/context_process_runtime.rb b/lib/execjs/pcruntime/context_process_runtime.rb
index 1acf8c3..00a7efb 100644
--- a/lib/execjs/pcruntime/context_process_runtime.rb
+++ b/lib/execjs/pcruntime/context_process_runtime.rb
@@ -5,6 +5,7 @@
 require 'json'
 require 'net/protocol'
 require 'net/http'
+require 'shellwords'
 
 module ExecJS
   module PCRuntime