--- old/src/java.desktop/unix/native/libawt_xawt/awt/swing_GTKEngine.c	2019-03-28 21:29:50.155617962 +0900
+++ new/src/java.desktop/unix/native/libawt_xawt/awt/swing_GTKEngine.c	2019-03-28 21:29:49.795617962 +0900
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -28,7 +28,7 @@
 #include "com_sun_java_swing_plaf_gtk_GTKEngine.h"
 
 /* Static buffer for conversion from java.lang.String to UTF-8 */
-static char conversionBuffer[CONV_BUFFER_SIZE];
+static char conversionBuffer[(CONV_BUFFER_SIZE - 1) * 3 + 1];
 
 const char *getStrFor(JNIEnv *env, jstring val)
 {