diff --git a/gc.c b/gc.c
index 220ae14d91..d8df0278fd 100644
--- a/gc.c
+++ b/gc.c
@@ -7358,8 +7358,10 @@ gc_mark_children(rb_objspace_t *objspace, VALUE obj)
       case T_FLOAT:
       case T_BIGNUM:
       case T_SYMBOL:
-        /* Not immediates, but does not have references and singleton
-         * class */
+        /* Not immediates, but does not have references and singleton class.
+         *
+         * RSYMBOL(obj)->fstr intentionally not marked. See log for 96815f1e
+         * ("symbol.c: remove rb_gc_mark_symbols()") */
         return;
 
       case T_NIL: