diff --git a/fun_with_bison/egg.xml b/fun_with_bison/egg.xml
index e8e717ffc07b1e7ba2102f7b823244c4f8211275..8c992be2dbbbf03e49e24a39fd8e2e222ee88729 100644
--- a/fun_with_bison/egg.xml
+++ b/fun_with_bison/egg.xml
@@ -41,7 +41,7 @@
           <symbol>FACTOR</symbol>
         </rhs>
       </rule>
-      <rule number="5" usefulness="useful">
+      <rule number="50" usefulness="useful">
         <lhs>FACTOR</lhs>
         <rhs>
           <symbol>OPENPAREN</symbol>