diff --git a/lib/sippy_cup/runner.rb b/lib/sippy_cup/runner.rb
index 7ffeaa4..63d7518 100644
--- a/lib/sippy_cup/runner.rb
+++ b/lib/sippy_cup/runner.rb
@@ -23,7 +23,7 @@ def initialize(scenario, opts = {})
       @scenario = scenario
       @scenario_options = @scenario.scenario_options
 
-      defaults = { full_sipp_output: true, sudo: true }
+      defaults = { full_sipp_output: true, sudo: true, trace_err: nil }
       @options = defaults.merge(opts)
 
       @command = @options[:command]
@@ -92,6 +92,7 @@ def command
         command_options.each_pair do |key, value|
           command << (value ? " -#{key} #{value}" : " -#{key}")
         end
+        command << " -trace_err"
         command << " #{@scenario_options[:destination]}"
       end
     end
diff --git a/lib/sippy_cup/scenario.rb b/lib/sippy_cup/scenario.rb
index 7073c9a..aaf98da 100644
--- a/lib/sippy_cup/scenario.rb
+++ b/lib/sippy_cup/scenario.rb
@@ -812,8 +812,8 @@ def send_bye_using_contact(opts = {})
 BYE [next_url] SIP/2.0
 Via: SIP/2.0/[transport] #{@adv_ip}:[local_port];rport;branch=[branch]
 [routes]
-To: "#{@from_user}" <sip:#{@from_user}@10.231.56.206:5090>;tag=[call_number]
-From: "#{@to_user}" <sip:#{@to_user}@stage.tncp.textnow.com>;tag=[call_number]
+To: "#{@from_user}" <sip:#{@from_user}@10.231.56.206:5090>[from_tag_param]
+From: "#{@to_user}" <sip:#{@to_user}@stage.tncp.textnow.com>[to_tag_param]
 [last_Call-ID:]
 Contact: <sip:#{@adv_ip};transport=[transport]>
 Max-Forwards: 100