diff --git a/scsh/rx/packages.scm b/scsh/rx/packages.scm
index 45d2907..9059149 100644
--- a/scsh/rx/packages.scm
+++ b/scsh/rx/packages.scm
@@ -164,9 +164,9 @@
   (compound-interface posix-re-interface
 		      basic-re-interface
 		      (export (regexp-match? (proc (:value) :boolean))
-			      (match:start (proc (:value :exact-integer) :value))
-			      (match:end   (proc (:value :exact-integer) :value))
-			      (match:substring (proc (:value :exact-integer) :value))
+			      (match:start (proc (:value &opt :exact-integer) :value))
+			      (match:end   (proc (:value &opt :exact-integer) :value))
+			      (match:substring (proc (:value &opt :exact-integer) :value))
 			      (clean-up-cres (proc () :unspecific))
 			      (regexp-search (proc (:value :string &opt :exact-integer)
 						   :value))