diff --git a/ChangeLog b/ChangeLog
index 987fda39f2..8563299b33 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Apr 20 21:32:11 2011  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* ext/date/date_strptime.c (date__strptime_internal): do not
+	  overwrite local variables.
+
 Wed Apr 20 14:41:28 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* string.c (rb_str_each_line): check string's length when compare
diff --git a/ext/date/date_strptime.c b/ext/date/date_strptime.c
index 27f0893efc..548e6a656d 100644
--- a/ext/date/date_strptime.c
+++ b/ext/date/date_strptime.c
@@ -576,6 +576,7 @@ date__strptime_internal(const char *str, size_t slen,
 		    }
 
 		    b = rb_backref_get();
+		    rb_match_busy(b);
 		    m = f_match(pat, rb_usascii_str_new2(&str[si]));
 
 		    if (!NIL_P(m)) {