diff --git a/s48/concurrency/packages.scm b/s48/concurrency/packages.scm
index d167740..b1da288 100644
--- a/s48/concurrency/packages.scm
+++ b/s48/concurrency/packages.scm
@@ -1,4 +1,4 @@
-(define-structure semaphores 
+(define-structure semaphores semaphores-interface
   (open scheme
 	locks
 	with-lock