diff --git a/lib/execjs/external_runtime.rb b/lib/execjs/external_runtime.rb
index 8a924d6..2133ce3 100644
--- a/lib/execjs/external_runtime.rb
+++ b/lib/execjs/external_runtime.rb
@@ -120,20 +120,25 @@ def binary
         @binary ||= which(@command)
       end
 
-      def locate_executable(cmd)
-        if ExecJS.windows? && File.extname(cmd) == ""
-          cmd << ".exe"
-        end
-
-        if File.executable? cmd
-          cmd
-        else
-          path = ENV['PATH'].split(File::PATH_SEPARATOR).find { |p|
-            full_path = File.join(p, cmd)
-            File.executable?(full_path) && File.file?(full_path)
+      def locate_executable(command)
+        commands = Array(command)
+        if ExecJS.windows? && File.extname(command) == ""
+          ENV['PATHEXT'].split(File::PATH_SEPARATOR).each { |p|
+            commands << (command + p)
           }
-          path && File.expand_path(cmd, path)
         end
+
+        commands.find { |cmd|
+          if File.executable? cmd
+            cmd
+          else
+            path = ENV['PATH'].split(File::PATH_SEPARATOR).find { |p|
+              full_path = File.join(p, cmd)
+              File.executable?(full_path) && File.file?(full_path)
+            }
+            path && File.expand_path(cmd, path)
+          end
+        }
       end
 
     protected