Index: src/main/java/common/javax/swing/JTextPane.java =================================================================== --- src/main/java/common/javax/swing/JTextPane.java (revision 503603) +++ src/main/java/common/javax/swing/JTextPane.java (working copy) @@ -53,6 +53,10 @@ public JTextPane(final StyledDocument doc) { this(); + + if (doc == null) { + throw new NullPointerException(); + } } public String getUIClassID() {