diff --git a/lib/puppet/util.rb b/lib/puppet/util.rb
index 06c7b11815..66be0f7da3 100644
--- a/lib/puppet/util.rb
+++ b/lib/puppet/util.rb
@@ -479,7 +479,7 @@ def safe_posix_fork(stdin = $stdin, stdout = $stdout, stderr = $stderr, &block)
 
       begin
         Dir.foreach('/proc/self/fd') do |f|
-          if f != '.' && f != '..' && f.to_i >= 3
+          if %{^\d+$}.match?(f) && f.to_i >= 3
             begin
               IO.new(f.to_i).close
             rescue