Created attachment 194759 [details] Zip of two files, extension and sample file This sample extension implements one formula =INCREMENTBYONE(x), simple increment of the number x by one. Ty reproduce: 1. Install 7.3.7 version of the LibreOffice 2. Install the extension 3. Open the attached "sample.xlsx" file Expected Result: A1 -> 2 Actual Result: A1 -> 2 4. Install any other version ( I tried 7.4.7 and 24.2 ) of the LibreOffice 5. Install the extension 6. Open the attached "sample.xlsx" file Expected Result: A1 -> 2 Actual Result: A1 -> #NAME? Attached is sample.xlsx, which was created by MS Excel.