diff --git a/src/chcm-elementary-op.lisp b/src/chcm-elementary-op.lisp
index b7b6bfb..5424f6e 100644
--- a/src/chcm-elementary-op.lisp
+++ b/src/chcm-elementary-op.lisp
@@ -7,6 +7,7 @@
 (PROVIDE "chcm-elementary-op")
 
 (DEFUN Z-CHCM ()
+  "Build the unit chain complex."
   (the chain-complex
        (build-chcm
 	:cmpr #'(lambda (gnrt1 gnrt2)