diff --git a/ChangeLog b/ChangeLog
index 0bd05ff231..ee386b3758 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Nov 18 20:47:41 2007  Tanaka Akira  <akr@fsij.org>
+
+	* marshal.c (mark_dump_arg): it may be called after dump_ensure.
+
 Sun Nov 18 18:27:47 2007  Tanaka Akira  <akr@fsij.org>
 
 	* time.c (time_minus): fix Time.at(2**60+1) - Time.at(2**60).
diff --git a/marshal.c b/marshal.c
index 1d883bfdd6..23669b9290 100644
--- a/marshal.c
+++ b/marshal.c
@@ -153,6 +153,8 @@ static void
 mark_dump_arg(void *ptr)
 {
     struct dump_arg *p = ptr;
+    if (!ptr)
+        return;
     rb_mark_set(p->data);
     rb_mark_hash(p->compat_tbl);
 }