Management Change/Compensation (Form 8-K)

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On June 5, 2026, Dennis Klaeser, a member of the Board of Directors (the "Board") of Old Second Bancorp, Inc. ("Old Second") and the Board of Directors (the "Bank Board") of its subsidiary bank, Old Second National Bank, notified Old Second of his resignation from the Board and Bank Board. Mr. Klaeser stated in his resignation letter that "I am honored to have served on the board of the company over the past 5 years as it has grown and developed into the bank it is today." James E. Eccher, Chairman and Chief Executive Officer of Old Second, stated, "we are grateful to Dennis and his service to Old Second, and we wish him well in his future endeavors." Mr. Klaeser's resignation was effective immediately and is not the result of any disagreement with Old Second. Mr. Klaeser served on the Executive Committee, the Audit Committee, the Compensation Committee, the Risk Committee and the Capital Committee. He has been a Board member since 2021, and Old Second appreciates his contributions during his tenure.

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Mr. Klaeser served as a Class II director with a term expiring at the Old Second's 2027 annual meeting. Old Second does not anticipate immediately filling the vacancy on the Board caused by Mr. Klaeser's resignation and will reduce the size of the Board by one member.

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