diff --git a/INSTALL b/INSTALL
index 89e77129f..8d4c44123 100644
--- a/INSTALL
+++ b/INSTALL
@@ -22,6 +22,10 @@ INSTALL NOTES
 
    NOTE2: if you use AFS, you need to run configure with --with-AFS
 
+   NOTE3: if you use kerberos version 4 you need to run configure
+   with --with-kerb4.  This has only been tested with the Cygnus
+   kerberos package (CNS) but should work for vanilla kerberos too.
+
 1) Read the OPTIONS file and then edit options.h to enable/disable the
    options you may or may not want.  You should not have to edit
    sudo.h or config.h.