diff --git a/autotest/JsonEmoticon/JsonEmoticon.cpp b/autotest/JsonEmoticon/JsonEmoticon.cpp
index 4a4538c5c..1f4c769fe 100644
--- a/autotest/JsonEmoticon/JsonEmoticon.cpp
+++ b/autotest/JsonEmoticon/JsonEmoticon.cpp
@@ -37,5 +37,9 @@ CONSOLE_APP_MAIN
 	ASSERT(text2 == text);
 	ASSERT(ToUtf32(text2) == h);
 	
+	String h127;
+	h127.Cat(127);
+	ASSERT(AsJSON(h127) == "\"\\u007F\"");
+	
 	LOG("=================== OK");
 }