diff --git a/test/sipp.js b/test/sipp.js
index 16b7363..8133894 100644
--- a/test/sipp.js
+++ b/test/sipp.js
@@ -67,8 +67,8 @@ obj.sippUac = (file, opts) => {
       debug(`stdout: ${data}`);
       addOutput(data.toString());
     });
-    child_process.stdout.on('data', (data) => {
-      debug(`stdout: ${data}`);
+    child_process.stderr.on('data', (data) => {
+      debug(`stderr: ${data}`);
       addOutput(data.toString());
     });
   });