java.lang.NoClassDefFoundError: OsInfo

After upgrading to 10.2.0.5 following error could be seen when using opatch.

/opt/app/oracle/product/10.2.0/ent/OPatch/opatch version
Exception in thread "main" java.lang.NoClassDefFoundError: OsInfo
Invoking OPatch 10.2.0.4.9

OPatch Version: 10.2.0.4.9

OPatch succeeded.

Believe this is due to missing OsInfo class in the opatch binaries bundled with 10.2.0.5 upgrade software.
Download the latest opatch from metalink and unzip into affected oracle home and error should disappear.