Index: flag.c
===================================================================
--- flag.c	(revision 37777)
+++ flag.c	(revision 37778)
@@ -70,7 +70,7 @@
 		next = u->next;
 		free(u);
 	}
-	f->unknowns = NULL;
+	memset(f, 0, sizeof(pcb_flag_t));
 }
 
 int pcb_flag_eq(pcb_flag_t *f1, pcb_flag_t *f2)