diff --git a/test.py b/test.py
index a366b4d..7d21a23 100644
--- a/test.py
+++ b/test.py
@@ -36,6 +36,9 @@ class TestParser(TestCase):
         self.assertEqual(str(parser.parse("(+ '1 (* 3 2))")),
                          "(+ . ('1 . ((* . (3 . (2 . NIL))) . NIL)))")
 
+    def test_error_unclosed_list(self):
+        self.assertRaises(ValueError, parser.parse("(42"))
+
 
 if __name__ == '__main__':
     import unittest
diff --git a/wasp/parser/__init__.py b/wasp/parser/__init__.py
index 77f0c0b..c0aa650 100644
--- a/wasp/parser/__init__.py
+++ b/wasp/parser/__init__.py
@@ -18,8 +18,11 @@ pg = ParserGenerator(["QUOTE", "LPAREN", "RPAREN", "ATOM"],
 def error_handler(token):
     type = token.gettokentype()
     pos = token.getsourcepos()
-    raise ValueError("unexpected %s at (%s, %s)" %
-                     (type, pos.lineno, pos.colno))
+    if pos is None:
+        raise ValueError("unexpected %s" % type)
+    else:
+        raise ValueError("unexpected %s at (%s, %s)" %
+                        (type, pos.lineno, pos.colno))
 
 
 @pg.production("main : sexpr")