diff --git a/ChangeLog b/ChangeLog
index ded7aea0ab..9849711b37 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Feb  2 09:49:39 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm.c (vm_backtrace_each): progname is not available at
+	  initializing phase.
+
 Mon Feb  2 08:12:50 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/xmlrpc/server.rb (Server#serve): gets rid of hardcoded
diff --git a/vm.c b/vm.c
index daed3bc6c3..e73ba39d6a 100644
--- a/vm.c
+++ b/vm.c
@@ -692,7 +692,7 @@ vm_backtrace_each(rb_thread_t *th, int lev, rb_backtrace_iter_func *iter, void *
 {
     const rb_control_frame_t *limit_cfp = th->cfp;
     const rb_control_frame_t *cfp = (void *)(th->stack + th->stack_size);
-    const char *file;
+    const char *file = "ruby";
     int line_no = 0;
 
     cfp -= 2;
@@ -702,7 +702,7 @@ vm_backtrace_each(rb_thread_t *th, int lev, rb_backtrace_iter_func *iter, void *
 	}
     }
     limit_cfp = RUBY_VM_NEXT_CONTROL_FRAME(limit_cfp);
-    file = RSTRING_PTR(th->vm->progname);
+    if (th->vm->progname) file = RSTRING_PTR(th->vm->progname);
     while (cfp > limit_cfp) {
 	if (cfp->iseq != 0) {
 	    if (cfp->pc != 0) {