Index: src/main/java/common/javax/swing/JEditorPane.java =================================================================== --- src/main/java/common/javax/swing/JEditorPane.java (revision 490282) +++ src/main/java/common/javax/swing/JEditorPane.java (working copy) @@ -619,6 +619,10 @@ } public void setEditorKitForContentType(final String type, final EditorKit kit) { + if (type == null || kit == null) { + throw new NullPointerException(); + } + int index = localContentTypes.indexOf(contentType); if (index >= 0) { localContentTypes.remove(index);