[R] stepAIC error

[labbig]

i am trying to run stepwise regression for two models(lower,upper),
family=gamma
and i get the same error despite the models i use.

Error in UseMethod("extractAIC") : 
  no applicable method for 'extractAIC' applied to an object of class
"formula"
In addition: Warning message:
In nobs.default(object, use.fallback = TRUE) :
  no 'nobs' method is available

Any help?
Thanks

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