[API Comparator] Exceptions

I just tried the plugin to compare openapi.jar (3235 with 3273) and got
two exceptions:
UNKNOWN
java.lang.NoSuchFieldError: UNKNOWN
at
org.intellij.apiComparator.spi.markup.TreeItemType.]]>(TreeItemType.java:18)
at
org.intellij.apiComparator.spi.parsers.JarFileParser.performParse(JarFileParser.java:39)
at
org.intellij.apiComparator.spi.parsers.AbstractTreeParser.parse(AbstractTreeParser.java:158)
at
org.intellij.apiComparator.ComparatorDialog.parseJarFile(ComparatorDialog.java:242)
at
org.intellij.apiComparator.ComparatorDialog.access$000(ComparatorDialog.java:53)
at
org.intellij.apiComparator.ComparatorDialog$2.run(ComparatorDialog.java:196)
at
com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:60)
at
com.intellij.openapi.application.impl.ApplicationImpl$1MyThread.run(ApplicationImpl.java:10)

No message
java.lang.NoClassDefFoundError
at
org.intellij.apiComparator.spi.parsers.JarFileParser.performParse(JarFileParser.java:39)
at
org.intellij.apiComparator.spi.parsers.AbstractTreeParser.parse(AbstractTreeParser.java:158)
at
org.intellij.apiComparator.ComparatorDialog.parseJarFile(ComparatorDialog.java:242)
at
org.intellij.apiComparator.ComparatorDialog.access$000(ComparatorDialog.java:53)
at
org.intellij.apiComparator.ComparatorDialog$2.run(ComparatorDialog.java:196)
at
com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:60)
at
com.intellij.openapi.application.impl.ApplicationImpl$1MyThread.run(ApplicationImpl.java:10)