diff --git a/reference/spl/book.xml b/reference/spl/book.xml
index d430a8bc7..b69c22e37 100644
--- a/reference/spl/book.xml
+++ b/reference/spl/book.xml
@@ -18,7 +18,6 @@
   </para>
  </preface>
 
- &reference.spl.constants;
  &reference.spl.datastructures;
  &reference.spl.iterators;
  &reference.spl.interfaces;