Using 64-bit Java with Processing 1.5.1?

How can one use 64-bit Java with Processing 1.5.1 on a Mac?
I have moved the 64-bit version of Java to the top in the Java Preferences Panel,  yet Processing still starts with the 32-bit version.

How can one 'force' processing to use the 64-bit version?

Thank you very much for your help!