Using test,modmed on mixed effect models

[TanFuMiao]

I am trying to compare the mediation effect between two levels of my moderator using test.modmed(). However, it does not seem to work on lmer() models.

test.modmed(modmed.model,
covariates.1=list(sex=1),
covariates.2=list(sex=0),
sims = 5000)
Error in test.modmed.default(modmed.model, covariates.1 = list(sex = 1), :
currently no test.modmed method exists for the input object.

When I changed the model to lm(), it works fine, So I can't seem to figure out the issue.