The reason seems to be that the proxiedBeanType in ProxyFactory is Object.class

Stacktrace

Caused by: java.lang.RuntimeException: java.lang.SecurityException: class "my.package.MyImpl$1431353132$Proxy$_$$_WeldClientProxy"'s signer information does not match signer information of other classes in the same package
at org.jboss.weld.util.bytecode.ClassFileUtils.toClass(ClassFileUtils.java:101)
at org.jboss.weld.bean.proxy.ProxyFactory.createProxyClass(ProxyFactory.java:491)
at org.jboss.weld.bean.proxy.ProxyFactory.getProxyClass(ProxyFactory.java:364)
... 152 more
Caused by: java.lang.SecurityException: class "my.package.MyImpl$1431353132$Proxy$_$$_WeldClientProxy"'s signer information does not match signer information of other classes in the same package
at java.lang.ClassLoader.checkCerts(ClassLoader.java:898)
at java.lang.ClassLoader.preDefineClass(ClassLoader.java:668)
at java.lang.ClassLoader.defineClass(ClassLoader.java:761)
at sun.reflect.GeneratedMethodAccessor143.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.jboss.weld.util.bytecode.ClassFileUtils.toClass2(ClassFileUtils.java:108)
at org.jboss.weld.util.bytecode.ClassFileUtils.toClass(ClassFileUtils.java:97)