diff --git a/ChangeLog b/ChangeLog
index 6b35175e08..c9e7789f01 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Apr 26 15:42:59 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/json/generator/generator.c (convert_UTF8_to_JSON_ASCII): get rid
+	  of a warning.
+
 Mon Apr 26 13:11:57 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (ripper_get_value): escape Qundef.
diff --git a/ext/json/generator/generator.c b/ext/json/generator/generator.c
index 3d3620534b..043be606cb 100644
--- a/ext/json/generator/generator.c
+++ b/ext/json/generator/generator.c
@@ -172,7 +172,7 @@ static void convert_UTF8_to_JSON_ASCII(FBuffer *buffer, VALUE string)
                             fbuffer_append(buffer, "\\\"", 2);
                             break;
                         default:
-                            fbuffer_append_char(buffer, ch);
+                            fbuffer_append_char(buffer, (char)ch);
                             break;
                     }
                 } else {