diff --git a/lib/puppet/parser/functions/docker_run_flags.rb b/lib/puppet/parser/functions/docker_run_flags.rb
index fa342acb..64379ae7 100644
--- a/lib/puppet/parser/functions/docker_run_flags.rb
+++ b/lib/puppet/parser/functions/docker_run_flags.rb
@@ -22,10 +22,12 @@ module Puppet::Parser::Functions
       flags << "--restart '#{opts['restart']}'"
     end
 
-    if opts['net'].is_a? String
-      flags << "--net #{opts['net'].shellescape}"
-    elsif opts['net'].is_a? Array
-      flags << "--net #{opts['net'].join(' --net ').shellescape}"
+    if opts['net']
+      if opts['net'].is_a? String
+        flags << "--net #{opts['net'].shellescape}"
+      elsif opts['net'].is_a? Array
+        flags << "--net #{opts['net'].join(' --net ').shellescape}"
+      end
     end
 
     if opts['memory_limit']
diff --git a/manifests/run.pp b/manifests/run.pp
index 147cac87..4e3725b2 100644
--- a/manifests/run.pp
+++ b/manifests/run.pp
@@ -204,7 +204,7 @@
   Optional[Boolean]                       $use_name                          = false,
   Optional[Boolean]                       $running                           = true,
   Optional[Variant[String,Array]]         $volumes_from                      = [],
-  Variant[String,Array]                   $net                               = 'bridge',
+  Variant[String,Array,Undef]             $net                               = undef,
   Variant[String,Boolean]                 $username                          = false,
   Variant[String,Boolean]                 $hostname                          = false,
   Optional[Variant[String,Array]]         $env                               = [],