OLD SECOND BANCORP INC — Director's Dealing 2026

Feb 24, 2026

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: OLD SECOND BANCORP INC (OSBC)
CIK: 0000357173
Period of Report: 2026-02-17

Reporting Person: KLAESER DENNIS L (N/A)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2026-02-17	Restricted Stock Units	A	3121	—	Acquired	13672	Direct
2026-02-21	Restricted Stock Units	F	3077	$20.57	Disposed	10595	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Old Second Bancorp, Inc. Common Stock	7657	Direct
Old Second Bancorp, Inc. Common Stock	42000	Indirect

Footnotes

F1: These shares represent restricted stock units granted pursuant to the Old Second Bancorp, Inc. Long Term Incentive Plan. These shares have a three-year cliff vesting.

F2: Represents shares vested upon the third anniversary of the date of grant previously reported and are now issued and added to the reporting person's common stock holdings outright.

F3: Represents shares held in Mr. Klaeser's name outright.