rlm_sql post-auth variable bug?

Hi, In my AAA chain I have a module that *sometimes* adds a custom attribute (defined in my dictionary as ipaddr) called Auth-NAS. This module is called in the authorize section. Later on, in the post-auth session I have a SQL-module that has: postauth_query = "INSERT INTO ${postauth_table} (...) \ VALUES (.... \ '%{check:Auth-NAS:-0.0.0.0}', ...)" When run, and Auth-NAS is not present, it outputs: rlm_sql (sql-xxx) in sql_postauth: query is INSERT INTO table (...) ??VALUES (..., '=01', ...); Sometimes the '=01' is replaced by '255.255.255.255'. Is this a bug in some place or am I doing something wrong? Any ideas? Thanks in advance. Fernando.