diff --git a/lex.py b/lex.py
index a25d4a5..94f98da 100755
--- a/lex.py
+++ b/lex.py
@@ -207,7 +207,10 @@ class LazyPatternRule(Rule):
         self.pattern = pattern
         self.d       = {}
     def _compile(self, d):
-        self.re = re.compile(self.pattern % d, self.reflags)
+        try:
+            self.re = re.compile(self.pattern % d, self.reflags)
+        except:
+            self.re = re.compile(self.pattern)
         self.d  = d
     def match(self, lexer, parent):
         if self.d != parent.matchd: