Excel file containing UDF from an XLAM file keeps asking to “update links” when opened

I have written a UDF called TJOIN stored in an XLAM file. I have connected to this Add-In. The UDF works fine.

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The content of the UDF is nothing special either.
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However when opening the file containing this formula, Excel asks me if I want to update links. If I choose Edit Links, the XLAM file is shown in the list.

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If I break this link, the formula is turned to text only.

How can I stop Excel from asking me to update links upon opening this file?