diff --git a/ChangeLog b/ChangeLog
index f0b695ab2e..cdda576cd0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Tue Nov 30 16:29:19 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* vm_dump.c: undef HAVE_BACKTRACE when the OS is FreeBSD (in other
+	  words backtrace() is libexecinfo) and it is optimized.
+	  This temporary hack should be also applied to other libexecinfo
+	  environments.
+
 Tue Nov 30 16:23:23 2010  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* lib/net/http.rb: improve rdoc.
diff --git a/vm_dump.c b/vm_dump.c
index 278c4aab43..fd8f9e50c9 100644
--- a/vm_dump.c
+++ b/vm_dump.c
@@ -585,6 +585,9 @@ bugreport_backtrace(void *arg, VALUE file, int line, VALUE method)
     return 0;
 }
 
+#if defined(__FreeBSD__) && defined(__OPTIMIZE__)
+#undef HAVE_BACKTRACE
+#endif
 #if HAVE_BACKTRACE
 # include <execinfo.h>
 #elif defined(_WIN32)