This is likely caused by the recent update to Qt 5.15.1, and seems to be fixed upstream:
https://github.com/openstreetmap/merkaartor/commit/e72553a7ea2c7ba0634cc3afcd27a9f7cfef089c Jerome, will you take care of this? Kind Regards, Bas -- GPG Key ID: 4096R/6750F10AE88D4AF1 Fingerprint: 8182 DE41 7056 408D 6146 50D1 6750 F10A E88D 4AF1