diff --git a/myhdl/_ShadowSignal.py b/myhdl/_ShadowSignal.py
index 5b091f81..c1a4acac 100644
--- a/myhdl/_ShadowSignal.py
+++ b/myhdl/_ShadowSignal.py
@@ -26,6 +26,7 @@ from __future__ import absolute_import
 import warnings
 from copy import deepcopy
 
+from myhdl._compat import long
 from myhdl._Signal import _Signal
 from myhdl._Waiter import _SignalWaiter, _SignalTupleWaiter
 from myhdl._intbv import intbv
@@ -148,7 +149,7 @@ class ConcatSignal(_ShadowSignal):
                 v = long(a, 2)
             else:
                 raise TypeError("ConcatSignal: inappropriate argument type: %s" \
-                                % type(arg))
+                                % type(a))
             nrbits += w
             val = val << w | v & (long(1) << w)-1
         self._initval = val
diff --git a/myhdl/test/core/test_ShadowSignal.py b/myhdl/test/core/test_ShadowSignal.py
index 3430a3d7..c6b6055d 100644
--- a/myhdl/test/core/test_ShadowSignal.py
+++ b/myhdl/test/core/test_ShadowSignal.py
@@ -1,5 +1,6 @@
 from __future__ import absolute_import
 from myhdl import *
+from myhdl._compat import long
 
 def bench_SliceSignal():