Donald Pilmer - 31 Dec 2025 Form 4 Insider Report for OLD SECOND BANCORP INC (OSBC)

Role: EVP
Signature: /s/ Shirley Cantrell, Attorney-in-Fact
Issuer symbol: OSBC
Transactions as of: 31 Dec 2025
Net transactions value: $0
Form type: 4
Filing time: 05 Jan 2026, 18:13:51 UTC
Previous filing: 01 Oct 2025
Next filing: 24 Feb 2026
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Pilmer Donald	EVP	37 S. RIVER ST., AURORA	/s/ Shirley Cantrell, Attorney-in-Fact	05 Jan 2026	0001673321

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	OSBC	Old Second Bancorp, Inc. Common Stock	Other	$0	+15	+0.38%	$0.000000	4,010	31 Dec 2025	By 401-K Plan	F1
holding	OSBC	Old Second Bancorp, Inc. Common Stock						182	31 Dec 2025	By Profit Sharing Plan
holding	OSBC	Old Second Bancorp, Inc. Common Stock						1,450	31 Dec 2025	Spouse's IRA	F2
holding	OSBC	Old Second Bancorp, Inc. Common Stock						63,135	31 Dec 2025	Direct
holding	OSBC	Restricted Stock Units						38,718	31 Dec 2025	Direct

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Of this total, 15 shares were allocated during the fourth quarter pursuant to the Old Second Bancorp, Inc. Employee Savings Plan & Trust. Information herein was provided by the Plan Trustee as of 12-31-25.
F2	These shares are held in spouse's IRA for which Mr. Pilmer is listed as a beneficiary.