Index: src/main/java/common/javax/swing/JComponent.java =================================================================== --- src/main/java/common/javax/swing/JComponent.java (revision 490924) +++ src/main/java/common/javax/swing/JComponent.java (working copy) @@ -481,6 +481,10 @@ } public final void putClientProperty(Object key, Object value) { + if (key == null) { + throw new NullPointerException(); + } + Object oldValue = (value != null) ? clientProperties.put(key, value) : clientProperties .remove(key); if (oldValue != value) {