diff --git a/ChangeLog b/ChangeLog
index 2887de5bcb..c7b66e47c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Oct  7 16:42:28 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* marshal.c (mark_dump_arg, mark_load_arg): ignore already cleaned
+	  data.  [ruby-core:25969]
+
+	* marshal.c (clear_dump_arg, clear_load_arg): clear freed fields.
+
 Wed Oct  7 16:06:30 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/ruby.h (rb_long2int): evalates the argument only
diff --git a/marshal.c b/marshal.c
index 8424639287..58128ef0d5 100644
--- a/marshal.c
+++ b/marshal.c
@@ -162,7 +162,7 @@ static void
 mark_dump_arg(void *ptr)
 {
     struct dump_arg *p = ptr;
-    if (!ptr)
+    if (!p->symbols)
         return;
     rb_mark_set(p->data);
     rb_mark_hash(p->compat_tbl);
@@ -850,7 +850,9 @@ clear_dump_arg(struct dump_arg *arg)
     st_free_table(arg->symbols);
     arg->symbols = 0;
     st_free_table(arg->data);
+    arg->data = 0;
     st_free_table(arg->compat_tbl);
+    arg->compat_tbl = 0;
     if (arg->encodings) {
 	st_free_table(arg->encodings);
 	arg->encodings = 0;
@@ -974,7 +976,7 @@ static void
 mark_load_arg(void *ptr)
 {
     struct load_arg *p = ptr;
-    if (!ptr)
+    if (!p->symbols)
         return;
     rb_mark_tbl(p->data);
     rb_mark_hash(p->compat_tbl);
@@ -1714,7 +1716,9 @@ clear_load_arg(struct load_arg *arg)
     st_free_table(arg->symbols);
     arg->symbols = 0;
     st_free_table(arg->data);
+    arg->data = 0;
     st_free_table(arg->compat_tbl);
+    arg->compat_tbl = 0;
 }
 
 /*