sun.security.rsa.RSAPrivateCrtKeyImpl cannot be cast to javax.crypto.SecretKey

When I used ENCRYPT with key_store like this:
<config xmlns="urn:org:jgroups" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/JGroups-3.3.xsd">
<TCP />
<MPING />
<MERGE2 />
<FD />
<VERIFY_SUSPECT />
<ENCRYPT key_store_name="server.keystore" store_password="changeit" alias="tomcat"/>
<pbcast.NAKACK />
<UNICAST3 />
<pbcast.GMS />
<UFC />
<MFC />
<STATS />
<pbcast.STATE_SOCK />
</config>

When I start the first Cluster it is OK, but when I start the second Cluster it throw:
Exception in thread "main" java.lang.ClassCastException: sun.security.rsa.RSAPrivateCrtKeyImpl cannot be cast to javax.crypto.SecretKey
at org.jgroups.protocols.ENCRYPT.initConfiguredKey(ENCRYPT.java:274)
at org.jgroups.protocols.ENCRYPT.init(ENCRYPT.java:234)
at org.jgroups.stack.ProtocolStack.initProtocolStack(ProtocolStack.java:848)
at org.jgroups.stack.ProtocolStack.setup(ProtocolStack.java:467)
at org.jgroups.JChannel.init(JChannel.java:830)
at org.jgroups.JChannel.<init>(JChannel.java:158)
at org.jgroups.JChannel.<init>(JChannel.java:138)