diff --git a/lib/tasks/exec_command.rake b/lib/tasks/exec_command.rake
index 08fbe2f..ee7217d 100644
--- a/lib/tasks/exec_command.rake
+++ b/lib/tasks/exec_command.rake
@@ -157,7 +157,11 @@ namespace :exec_commands do
                 update_infos_for_exec(data)
               end
             else
-              outputs[-1] += data.to_s rescue ""
+              if outputs.count == 0
+                outputs.push(data.to_s)
+              else
+                outputs[-1] += (data.to_s rescue "")
+              end
               if update
                 update_thread_infos_for_exec(data,true) if @flag
                 update_infos_for_exec(data,true)