diff --git a/ChangeLog b/ChangeLog
index c0731831b6..882e7a3a60 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Jan 15 13:21:50 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/json/parser/parser.rl (json_string_unescape): workaround fix
+	  for over optimization of GCC 4.7. [ruby-core:42085] [Bug #5888]
+	  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51862
+
 Sat Jan 14 22:24:09 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/dl/callback/mkcallback.rb (gencallback): suppress unused
diff --git a/ext/json/parser/parser.c b/ext/json/parser/parser.c
index d1d14c79ca..1773616463 100644
--- a/ext/json/parser/parser.c
+++ b/ext/json/parser/parser.c
@@ -1293,6 +1293,7 @@ static VALUE json_string_unescape(VALUE result, char *string, char *stringEnd)
 {
     char *p = string, *pe = string, *unescape;
     int unescape_len;
+    char buf[4];
 
     while (pe < stringEnd) {
         if (*pe == '\\') {
@@ -1325,7 +1326,6 @@ static VALUE json_string_unescape(VALUE result, char *string, char *stringEnd)
                     if (pe > stringEnd - 4) {
                         return Qnil;
                     } else {
-                        char buf[4];
                         UTF32 ch = unescape_unicode((unsigned char *) ++pe);
                         pe += 3;
                         if (UNI_SUR_HIGH_START == (ch & 0xFC00)) {
diff --git a/ext/json/parser/parser.rl b/ext/json/parser/parser.rl
index e7d47e1589..33e775ce72 100644
--- a/ext/json/parser/parser.rl
+++ b/ext/json/parser/parser.rl
@@ -393,6 +393,7 @@ static VALUE json_string_unescape(VALUE result, char *string, char *stringEnd)
 {
     char *p = string, *pe = string, *unescape;
     int unescape_len;
+    char buf[4];
 
     while (pe < stringEnd) {
         if (*pe == '\\') {
@@ -425,7 +426,6 @@ static VALUE json_string_unescape(VALUE result, char *string, char *stringEnd)
                     if (pe > stringEnd - 4) {
                         return Qnil;
                     } else {
-                        char buf[4];
                         UTF32 ch = unescape_unicode((unsigned char *) ++pe);
                         pe += 3;
                         if (UNI_SUR_HIGH_START == (ch & 0xFC00)) {