How to I change a method of an interface using mixins?

So I have set up a mixin environment correctly (using sponge of course), and I want to change the isEmptyBlock method of LevelReader, I am using this code: in: MixinLevelReader

package net.iateminecraft.jetpacksfix.mixin;

import com.mojang.logging.LogUtils;
import net.minecraft.core.BlockPos;
import org.slf4j.Logger;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.Unique;
import org.spongepowered.asm.mixin.injection.At;
import org.spongepowered.asm.mixin.injection.Inject;
import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;

public abstract class MixinLevelReader {
    private static final Logger LOGGER = LogUtils.getLogger();
    LevelAccessor world = (LevelAccessor) (Object) this;

    @Inject(at = @At("HEAD"), method = "isEmptyBlock(Lnet/minecraft/core/BlockPos;)Z", cancellable = true)
    private void isEmptyBlock(BlockPos blockposition, CallbackInfoReturnable<Boolean> callback) {;

It will compile fine when I run ./gradlew :build, but as soon as I do ./gradlew :runClient it errors with: Caused by: org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException: @Mixin target type mismatch: is an interface in org.spongepowered.asm.mixin.transformer.MixinInfo$SubType$Standard@75b6dd5b
After some research it means that I’m trying to mixin with an interface which is incorrect, so how do I do it?