带有[java/lang/String]的Proguard警告

我面临proguard的问题。我在proguard中有一些规则,其中之一是:

-keep class org.jmrtd.** { *; }
-dontwarn org.jmrtd.**

但我在建造时收到了这个警告

Unexpected error while performing partial evaluation:
  Class       = [org/jmrtd/MRTDFileSystem]
  Method      = [readBinary(II)[B]
  Exception   = [java.lang.IllegalArgumentException] (Can't find common super class of [java/lang/String] (with 2 known super classes) and [org/jmrtd/MRTDFileSystem$MRTDFileInfo] (with 1 known super classes))
Unexpected error while preverifying:
  Class       = [org/jmrtd/MRTDFileSystem]
  Method      = [readBinary(II)[B]
  Exception   = [java.lang.IllegalArgumentException] (Can't find common super class of [java/lang/String] (with 2 known super classes) and [org/jmrtd/MRTDFileSystem$MRTDFileInfo] (with 1 known super classes))

有人能帮我吗? 非常感谢。