diff --git a/config.hin b/config.hin
index e0f77a347..ed4e14da6 100644
--- a/config.hin
+++ b/config.hin
@@ -25,6 +25,7 @@
 
 /* Define the default level of POSIX conformance for these tools. The value is
    of the form YYYYMM, specifying the year and month the standard was adopted.
+   Unless explicitly selected at configure-time, this symbol is not defined.
    */
 #undef DEFAULT_POSIX2_VERSION