The Holland defender is inside the final year of his Villa deal.
Lambert said in The Sun: "Ron is not only an Aston Villa player, he is our captain.
"He has one year remaining on his contract and he is staying here. We will be talking with him in due course about extending his deal and we are confident those talks will be positive.
"Ron has always said that he is really happy here and has done nothing to suggest anything has changed.
"None of this speculation is coming from him, or anyone connected with him.
"We aren't selling. It is as simple as that."
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