diff --git a/src/py65/tests/utils/test_addressing.py b/src/py65/tests/utils/test_addressing.py
index bc1d624..2741c23 100644
--- a/src/py65/tests/utils/test_addressing.py
+++ b/src/py65/tests/utils/test_addressing.py
@@ -3,6 +3,22 @@ import sys
 from py65.utils.addressing import AddressParser
 
 class AddressParserTests(unittest.TestCase):
+  def test_maxwidth_can_be_set_in_constructor(self):
+    parser = AddressParser(maxwidth=24)
+    self.assertEqual(24, parser.maxwidth)
+    self.assertEqual(0xFFFFFF, parser._maxaddr)
+
+  def test_maxwidth_defaults_to_16_bits(self):
+    parser = AddressParser()
+    self.assertEqual(16, parser.maxwidth)                                   
+    self.assertEqual(0xFFFF, parser._maxaddr)
+
+  def test_maxwidth_setter(self):
+    parser = AddressParser()
+    parser.maxwidth = 24
+    self.assertEqual(24, parser.maxwidth)
+    self.assertEqual(0xFFFFFF, parser._maxaddr)       
+
   def test_number_hex_literal(self):
     parser = AddressParser()
     self.assertEqual(49152, parser.number('$c000'))
@@ -81,6 +97,17 @@ class AddressParserTests(unittest.TestCase):
     except KeyError, why:
       self.assertEqual('Label not found: bad_label', why[0])    
 
+  def test_number_truncates_address_at_maxwidth_16(self):
+    parser = AddressParser()
+    parser.labels = {'foo': 0xFFFF}
+    self.assertEqual(0xFFFF, parser.number('foo+5'))
+
+  def test_number_truncates_address_at_maxwidth_24(self):
+    parser = AddressParser()
+    parser.maxwidth = 24
+    parser.labels = {'foo': 0xFFFFFF}
+    self.assertEqual(0xFFFFFF, parser.number('foo+5'))
+
   def test_label_for_returns_label(self):
     parser = AddressParser(labels={'chrout':0xFFD2})
     self.assertEqual('chrout', parser.label_for(0xFFD2))
diff --git a/src/py65/utils/addressing.py b/src/py65/utils/addressing.py
index d331797..bc577d7 100644
--- a/src/py65/utils/addressing.py
+++ b/src/py65/utils/addressing.py
@@ -1,17 +1,28 @@
 import re
 
-class AddressParser:
+class AddressParser(object):
     """Parse user input into addresses or ranges of addresses.
     """
 
-    def __init__(self, radix=16, labels={}):
-        """Radix is the default radix to use when one is not specified
+    def __init__(self, maxwidth=16, radix=16, labels={}):
+        """Maxwidth is the maximum width of an address in bits.
+        Radix is the default radix to use when one is not specified
         as a prefix of any input.  Labels are a dictionary of label
         names that can be substituted for addresses.
         """
         self.radix = radix
         self.labels = labels
+        self.maxwidth = maxwidth
+        
+    def _get_maxwidth(self):
+        return self._maxwidth    
 
+    def _set_maxwidth(self, width):
+        self._maxwidth = width
+        self._maxaddr = pow(2, width) - 1
+
+    maxwidth = property(_get_maxwidth, _set_maxwidth)
+              
     def label_for(self, address, default=None):
         """Given an address, return the corresponding label or a default.
         """
@@ -53,8 +64,8 @@ class AddressParser:
 
                 if address < 0:
                     address = 0
-                if address > 0xFFFF:
-                    address = 0xFFFF
+                if address > self._maxaddr:
+                    address = self._maxaddr
                 return address
 
             else: