diff --git a/pySim/exceptions.py b/pySim/exceptions.py
index c0cf1e7..5d30f76 100644
--- a/pySim/exceptions.py
+++ b/pySim/exceptions.py
@@ -5,6 +5,7 @@
 
 #
 # Copyright (C) 2009-2010  Sylvain Munaut <tnt@246tNt.com>
+# Copyright (C) 2021 Harald Welte <laforge@osmocom.org>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -36,3 +37,12 @@
 
 class ReaderError(Exception):
 	pass
+
+class SwMatchError(Exception):
+	"""Raised when an operation specifies an expected SW but the actual SW from
+	   the card doesn't match."""
+	def __init__(self, sw_actual, sw_expected):
+		self.sw_actual = sw_actual
+		self.sw_expected = sw_expected
+	def __str__(self):
+		return "SW match failed! Expected %s and got %s." % (self.sw_expected, self.sw_actual)