[R] lmer Error message

Does anybody knows what this error message means: Error in object$terms : $ operator not defined for this S4 class I have peformed the following steps: library(lattice) library(Matrix) library(lme4) inkm inkm$Gamie glm.incm drop1(glm.incm,test="Ch") Error in object$terms : $ operato

[R] drop1: warning message

Dear R collegues, I am new to R and do not understad the warning messages, which appear when I am trying to apply type III procedure to my glm: inkm$Gamie glm.inkmZ drop1(glm.inkmZ,test="Ch") Single term deletions Model: InkMb ~ IncStart + Vol + Gamie + PC1 + PC2 + PC3 + SpotsN + PC1:SpotsN