diff --git a/src/topten.c b/src/topten.c
index 84146e9ad..ec689abc4 100644
--- a/src/topten.c
+++ b/src/topten.c
@@ -30,7 +30,10 @@ static long final_fpos;
 
 #define newttentry() (struct toptenentry *) alloc(sizeof (struct toptenentry))
 #define dealloc_ttentry(ttent) free((genericptr_t) (ttent))
+#ifndef NAMSZ
+/* Changing NAMSZ can break your existing record/logfile */
 #define NAMSZ 10
+#endif
 #define DTHSZ 100
 #define ROLESZ 3