OpenJML with generics?

I have a class Edge.java. When I run it through OpenJML, this happens:

error: An internal JML error occurred, possibly recoverable. Please report the bug with as much information as you can. Reason: com.sun.tools.javac.code.Symbol$TypeSymbol cannot be cast to com.sun.tools.javac.code.Symbol$ClassSymbol

Weird thing is, I haven't even started to put in the jml notations.

My jdk is 1.7, openjml is current (re-downloaded both to make sure).

This is the command used to run openjml (following the example from the site): java -jar "E:\Downloads\openjml\openjml.jar" -esc -prover z3_4_3 -exec "E:\Downloads\z3-4.3.0-x64\bin\z3.exe" -noPurityCheck Test.java

Edit: I can confirm that even a very simple class with generics can cause this error:

public class Test<T> {
    T i;
}

Edge.java

public class Edge<K> implements Comparable<Edge<K>> {
    public K n1, n2;
    public int weight;

    public final int tiebreaker;
    public static int nextTiebreaker = 0;

    public Edge(K n1, K n2, int weight) {
        this.n1 = n1;
        this.n2 = n2;
        this.weight = weight;
        tiebreaker = nextTiebreaker++;
    }

    @Override
    public int compareTo(Edge<K> o) {
        if(this.weight > o.weight) return +1;
        if(this.weight < o.weight) return -1;

        return tiebreaker - o.tiebreaker; //Same cost, pick one to be the "larger" 
    }
}

The workaround that I found is to remove the -esc option (runs extended static checking). Not sure of the proper way to solve this.