"Object is not an instance of declaring class" when invoking a method with no args

I've been working with reflections for a while, but I've never seen this error before. As you can see down here:

            Object tileEntity = setAccessible(craftCreatureSpawnerClass.getSuperclass().getDeclaredMethod("getTileEntity")).invoke(cs);

I am invoking a method, which I've made accessible. CraftCreatureSpawner's the main class, and I get it's superclass. Inside it's superclass, there is a pretty important method, called getTileEntity, and I need what it's returning.

I appreciate all the help.