diff --git a/ChangeLog b/ChangeLog
index 63f6264e0b..ba27b9dd74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,4 @@
-Thu Apr 15 14:38:03 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Thu Apr 15 14:50:19 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* vm.c (vm_backtrace_each): get rid of use of malloc from signal
 	  handler by using ruby_engine_name.  [ruby-core:29497]
@@ -6,6 +6,8 @@ Thu Apr 15 14:38:03 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 	* vm_eval.c (print_backtrace): file may be nil when segfaulted in
 	  very early stage.
 
+	* vm_dump.c (bugreport_backtrace): ditto.
+
 Thu Apr 15 11:51:49 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* common.mk (help): small fix.
diff --git a/vm_dump.c b/vm_dump.c
index 0aa8dae570..7667cb616b 100644
--- a/vm_dump.c
+++ b/vm_dump.c
@@ -570,12 +570,18 @@ rb_vmdebug_thread_dump_state(VALUE self)
 static int
 bugreport_backtrace(void *arg, VALUE file, int line, VALUE method)
 {
+    const char *filename = NIL_P(file) ? "ruby" : RSTRING_PTR(file);
     if (!*(int *)arg) {
 	fprintf(stderr, "-- Ruby level backtrace information "
 		"----------------------------------------\n");
 	*(int *)arg = 1;
     }
-    fprintf(stderr, "%s:%d:in `%s'\n", RSTRING_PTR(file), line, RSTRING_PTR(method));
+    if (NIL_P(method)) {
+	fprintf(stderr, "%s:%d:in unknown method\n", filename, line);
+    }
+    else {
+	fprintf(stderr, "%s:%d:in `%s'\n", filename, line, RSTRING_PTR(method));
+    }
     return 0;
 }