Can't have custom mob with slime AI!

For some reason, I can't make my mob have the AI of a slime. Whenever I select the custom AI to be a slime, mcreator rejects it. Here is what the log says:

C:\Users\blah\MCreatorWorkspaces\frosted_isle\build\sources\main\java\net\mcreator\frosted_isle\MCreatorColdBlueSlime.java:83: error: incompatible types: EntityCustom cannot be converted to EntityCreature
            this.tasks.addTask(1, new EntityAIWander(this, 1));
                                                     ^
C:\Users\blah\MCreatorWorkspaces\frosted_isle\build\sources\main\java\net\mcreator\frosted_isle\MCreatorColdBlueSlime.java:87: error: incompatible types: EntityCustom cannot be converted to EntityCreature
            this.tasks.addTask(5, new EntityAIPanic(this, 1.2));
                                                    ^
C:\Users\blah\MCreatorWorkspaces\frosted_isle\build\sources\main\java\net\mcreator\frosted_isle\MCreatorColdBlueSlime.java:88: error: incompatible types: EntityCustom cannot be converted to EntityCreature
            this.targetTasks.addTask(6, new EntityAIHurtByTarget(this, false));
                                                                 ^
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3 errors

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
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BUILD FAILED in 1s