I have a plugin which uses PSI to chane an XmlTag's name (via setName). It usually works very well, but on one occasion (could not reproduce since) I have run into the following exception: java.lang.NullPointerException at com.intellij.psi.impl.source.tree.ChangeUtil.copyElement(ChangeUtil.java:232) at com.intellij.psi.impl.source.xml.XmlTagImpl$2.runInner(XmlTagImpl.java:1) at com.intellij.pom.impl.PomTransactionBase.run(PomTransactionBase.java:28) at com.intellij.pom.core.impl.PomModelImpl.runTransaction(PomModelImpl.java:34) at com.intellij.psi.impl.source.xml.XmlTagImpl.setName(XmlTagImpl.java:66) at org.mevenide.idea.psi.util.PsiUnnamedPropertyChangeListener$TagRenamerRunnable.run(PsiUnnamedPropertyChangeListener.java:342) at com.intellij.openapi.command.impl.CommandProcessorImpl.executeCommand(CommandProcessorImpl.java:122) at com.intellij.openapi.command.impl.CommandProcessorImpl.executeCommand(CommandProcessorImpl.java) at org.mevenide.idea.util.IDEUtils$1.run(IDEUtils.java:35) at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:168) at org.mevenide.idea.util.IDEUtils.runCommand(IDEUtils.java:33) at org.mevenide.idea.psi.util.PsiUnnamedPropertyChangeListener.renameProperty(PsiUnnamedPropertyChangeListener.java:98) at org.mevenide.idea.psi.support.AbstractPsiUnnamedPropertyObservable.renameProperty(AbstractPsiUnnamedPropertyObservable.java:51) at org.mevenide.idea.editor.pom.ui.dependencies.DependencyPropertiesTableModel.setValueAt(DependencyPropertiesTableModel.java:38) at javax.swing.JTable.setValueAt(JTable.java:1875) at javax.swing.JTable.editingStopped(JTable.java:3333) at javax.swing.AbstractCellEditor.fireEditingStopped(AbstractCellEditor.java:124) at javax.swing.DefaultCellEditor$EditorDelegate.stopCellEditing(DefaultCellEditor.java:329) at javax.swing.DefaultCellEditor.stopCellEditing(DefaultCellEditor.java:214) at javax.swing.JTable$GenericEditor.stopCellEditing(JTable.java:3677) at com.intellij.util.ui.Table.editCellAt(Table.java:110) at javax.swing.plaf.basic.BasicTableUI$Handler.adjustFocusAndSelection(BasicTableUI.java:922) at javax.swing.plaf.basic.BasicTableUI$Handler.mousePressed(BasicTableUI.java:889) at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:222) at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:221) at java.awt.Component.processMouseEvent(Component.java:5485) at javax.swing.JComponent.processMouseEvent(JComponent.java:3093) at java.awt.Component.processEvent(Component.java:5253) at java.awt.Container.processEvent(Container.java:1966) at java.awt.Component.dispatchEventImpl(Component.java:3955) at java.awt.Container.dispatchEventImpl(Container.java:2024) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3889) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822) at java.awt.Container.dispatchEventImpl(Container.java:2010) at java.awt.Window.dispatchEventImpl(Window.java:1774) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.EventQueue.dispatchEvent(EventQueue.java:463) at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:144) at com.intellij.ide.IdeEventQueue.a(IdeEventQueue.java:59) at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:82) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149) at java.awt.EventDispatchThread.run(EventDispatchThread.java:110) See http://www.intellij.net/forums/thread.jsp?forum=22&thread=148666&message=4882142&q=457863657074696f6e207768696c652063616c6c696e6720507369456c656d656e742e7365744e616d65#4882142 for details.