diff --git a/avocado/core/exceptions.py b/avocado/core/exceptions.py
index 7901b40cdc2beee76b42b7d666ff666c07475c8a..3f11a0962637b24c56036efea614f59a9c807a57 100644
--- a/avocado/core/exceptions.py
+++ b/avocado/core/exceptions.py
@@ -106,15 +106,18 @@ class TestWarn(TestBaseException):
 
 class CmdError(Exception):
 
-    def __init__(self, command, result):
+    def __init__(self, command=None, result=None):
         self.command = command
         self.result = result
 
     def __str__(self):
-        if self.result.exit_status is None:
-            msg = "Command '%s' failed and is not responding to signals"
-            msg %= self.command
+        if self.result is not None:
+            if self.result.exit_status is None:
+                msg = "Command '%s' failed and is not responding to signals"
+                msg %= self.command
+            else:
+                msg = "Command '%s' failed (rc=%d)"
+                msg %= (self.command, self.result.exit_status)
+            return msg
         else:
-            msg = "Command '%s' failed (rc=%d)"
-            msg %= (self.command, self.result.exit_status)
-        return msg
+            return "CmdError"