The platform-agnostic nature of Java is made possible thanks to the presence ofthe Java Virtual Machine (JVM) with a well defined set of bytecodes and libraryroutines. This requires the availability of a JVM for many different platforms,32-bit as well as 64-bit wide.During an effort to port the Jikes Research Virtual Machine (RVM) to the64-bit PowerPC, we stumbled into a number of problems that prove that the Javaspecification was designed with a 32-bit platform in mind and that prevent anefficient implementation on a 64-bit platform.All described problems boil down to the fact that all types have a fixed size, while it is in the nature of some types to automatically adapt to the word-size of the current platform.We would like to share those issues with the community, so that future SPEC designers can take into account these flaws. While Java declares to be platformindependent, we believe some aspects of the Java SPEC are designed too specific for a 32-bit platform.