diff --git a/collects/redex/private/underscore-allowed.rkt b/collects/redex/private/underscore-allowed.rkt
index 2db9e96a11..d43b75aecd 100644
--- a/collects/redex/private/underscore-allowed.rkt
+++ b/collects/redex/private/underscore-allowed.rkt
@@ -1,3 +1,3 @@
 #lang racket/base
 (provide underscore-allowed) 
-(define underscore-allowed '(any number string variable variable-not-otherwise-mentioned natural integer real))
+(define underscore-allowed '(any number string variable variable-not-otherwise-mentioned natural integer real boolean))