Hi, I have a Jython app that uses one pure Java class Foo. Calling import Foo in Jython leads to the "java.lang.UnsupportedClassVersionError: java.lang.UnsupportedClassVersionError: Bad version number in .class file" error ( no other info provided ) on OSX but not on linux. 

As far as I can tell, the class version matches the Jython runtime version:

# asking for version number from jython
$ jython -v
Jython 2.5.3b1 (2.5:5fa0a5810b25, Feb 22 2012, 12:39:02) 
[Java HotSpot(TM) Client VM (Apple Inc.)] on java1.5.0_30

# inspecting version number at runtime from within jythong
>>> import java.lang.System as System 
>>> System.getProperty('java.version')

# system java version
$ java -version
java version "1.5.0_30"

# system javac version
$ javac -version
javac 1.5.0_30

# inspecting compiled class ( this means 1.5 if I understand correctly )
$ javap -v Foo | grep version
  minor version: 0
  major version: 50

I'm not sure I can fix this on my own, since everything I know to check checks out. Maybe it is a bug? Have other people encountered this?