diff --git a/ch5/interpreter/interpreter.py b/ch5/interpreter/interpreter.py
index 453e053..84b8aee 100644
--- a/ch5/interpreter/interpreter.py
+++ b/ch5/interpreter/interpreter.py
@@ -150,7 +150,7 @@ def main():
             cmd, dev, arg = event.parseString(t)
             cmd_str = " ".join(cmd)
             dev_str = " ".join(dev)
-            arg_str = " ".join(cmd)
+            arg_str = " ".join(arg)
             num_arg = 0
             try:
                 # extract the numeric part