The wrapped_command has spaces which triggers Ruby to fork a system shell (with /bin/sh -c). This causes orphaned processes on some systems (i.e. Linux). Fix this by splitting the command using String#shellsplit and using ruby's splat operator (*) to pass discrete arguments to spawn.

lib/foreman/process.rb

@@ -1,4 +1,5 @@
 require "foreman"
+require "shellwords"
 
 class Foreman::Process
 
@@ -54,8 +55,8 @@ class Foreman::Process
       end
     elsif Foreman.jruby_18? || Foreman.ruby_18?
       require "posix/spawn"
-      wrapped_command = "#{Foreman.runner} -d '#{cwd}' -p -- #{command}"
+      wrapped_command = "#{Foreman.runner} -d '#{cwd}' -p -- #{expanded_command(env)}"
-      POSIX::Spawn.spawn env, wrapped_command, :out => output, :err => output
+      POSIX::Spawn.spawn(*spawn_args(env, wrapped_command.shellsplit, {:out => output, :err => output}))
     else
       wrapped_command = "#{Foreman.runner} -d '#{cwd}' -p -- #{command}"
       Process.spawn env, wrapped_command, :out => output, :err => output
@@ -114,4 +115,14 @@ class Foreman::Process
     File.expand_path(@options[:cwd] || ".")
   end
 
+private
+
+  def spawn_args(env, argv, options)
+    args = []
+    args << env
+    args += argv
+    args << options
+    args
+  end
+
 end