diff --git a/py65/monitor.py b/py65/monitor.py
index d1c7b5d..ff94663 100644
--- a/py65/monitor.py
+++ b/py65/monitor.py
@@ -107,7 +107,9 @@ class Monitor(cmd.Cmd):
             cmd = "load %s" % load_value
             self.onecmd(cmd)
 
-        if flag_mpu == True:
+        if (flag_mpu == True) or (flag_rom == True):
+            if mpu_value == "":
+                mpu_value = "6502"
             if self._get_mpu(mpu_value) is None:
                 mpus = list(self.Microprocessors.keys())
                 mpus.sort()