Fix for real this time!
import org.spongepowered.common.mixin.entityactivation.MixinEntity_Activation;
@NonnullByDefault
-@Mixin(EntityItem.class)
+@Mixin(value = EntityItem.class, priority = 1001)
public abstract class MixinEntityItem_Activation extends MixinEntity_Activation {
@Shadow public abstract ItemStack getItem();
