diff --git a/relational/parser.py b/relational/parser.py
index 30add2b..4fdc065 100644
--- a/relational/parser.py
+++ b/relational/parser.py
@@ -165,7 +165,7 @@ class Node (object):
                 self.child = node(expression[2 + i])
 
                 return
-        raise ParserException(u"Unable to parse tokens")
+        raise ParserException("Expected operator in '%s'" % ' '.join(expression))
         pass
 
     def toCode(self):