Error generating invokers using a declaration having a primitive type

When the value type of a declaration is primitive, the invokers created via mvel templating using that declaration cannot be compiled because they try to do an invalid cast from an Object to a primitive type, generating an error as it follows:

java.lang.AssertionError: Unable to generate rule invoker. : [Accumulate: input=[AND [[Pattern: id=null; objectType=MyObj]] ]]
org/drools/Rule_foo_3191b39fd6ce40eaac55301df07acc19AccumulateExpression0Invoker.java (19:754) : Cannot cast from Object to long