diff --git a/py65/monitor.py b/py65/monitor.py
index 5070317..88c8972 100644
--- a/py65/monitor.py
+++ b/py65/monitor.py
@@ -442,16 +442,21 @@ class Monitor(cmd.Cmd):
         self._output("Display a number in decimal, hex, octal, and binary.")
 
     def do_tilde(self, args):
+        if args == '':
+            return self.help_tilde()
+
         try:
             num = self._address_parser.number(args)
-        except ValueError:
-            self._output("Syntax error: %s" % args)
-            return
-
-        self._output("+%u" % num)
-        self._output("$" + self.byteFmt % num)
-        self._output("%04o" % num)
-        self._output(itoa(num, 2).zfill(8))
+            self._output("+%u" % num)
+            self._output("$" + self.byteFmt % num)
+            self._output("%04o" % num)
+            self._output(itoa(num, 2).zfill(8))
+        except KeyError:
+            self._output("Bad label: %s" % args)
+        except OverflowError:
+            self._output("Overflow error: %s" % args)
+        except SyntaxError:
+            self._output("Syntax error: %s" % statement)
 
     def help_registers(self):
         self._output("registers[<name>=<value> [, <name>=<value>]*]")
diff --git a/py65/tests/test_monitor.py b/py65/tests/test_monitor.py
index 1eae781..afbaad6 100644
--- a/py65/tests/test_monitor.py
+++ b/py65/tests/test_monitor.py
@@ -804,6 +804,14 @@ class MonitorTests(unittest.TestCase):
         expected = "+16\n$10\n0020\n00010000\n"
         self.assertTrue(out.startswith(expected))
 
+    def test_do_tilde_with_no_arg_shows_help(self):
+        stdout = StringIO()
+        mon = Monitor(stdout=stdout)
+        mon.do_tilde('')
+        out = stdout.getvalue()
+        expected = "~ <number>"
+        self.assertTrue(out.startswith(expected))
+
     def test_help_tilde(self):
         stdout = StringIO()
         mon = Monitor(stdout=stdout)