Index: dirlist.mk
===================================================================
--- dirlist.mk	(revision 2598)
+++ dirlist.mk	(working copy)
@@ -31,6 +31,7 @@
                 operation\polygonize \
                 operation\predicate \
                 operation\relate \
+                operation\union \
                 operation\valid \
                 planargraph \
                 planargraph\algorithm \