[Ant] Unable to find a javac compiler

BUILD FAILED
D:\web_dev\ant_build2.xml:16: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre6"

set JAVA_HOME=C:\Program Files\Java\jdk1.5.0_22