diff --git a/CVS_README b/CVS_README
index f39fc79..32d3209 100644
--- a/CVS_README
+++ b/CVS_README
@@ -35,7 +35,10 @@ To build Scsh, proceed as follows:
 
     This will take several minutes and generate the source code for
     the virtual machine and two images the Makefile relies
-    on. Furthermore the configure file will be generated.
+    on. Furthermore the configure file will be generated. This script
+    calls autoheader and autoconf from the GNU Autoconf package. You
+    will need a recent version of Autoconf. Version 2.53 is okay,
+    version 2.13 is too old.
 
 3.) Configure the system: