SEC FORM 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person ^*

YORK JILL E

(Last)

(First)

(Middle)

37 S. RIVER ST.

(Street)

AURORA

60506

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
OLD SECOND BANCORP INC [ OSBC ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
05/11/2021

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Old Second Bancorp, Inc. Common Stock	05/11/2021		L		14.2083 ⁽¹⁾	A	$ 14.08	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/11/2021		L		17.5446 ⁽¹⁾	A	$ 11.44	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	11/09/2021		L		14.5974 ⁽¹⁾	A	$ 13.81	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	02/08/2022		L		14.0252 ⁽¹⁾	A	$ 14.43	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	05/10/2022		L		14.3579 ⁽¹⁾	A	$ 14.14	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/09/2022		L		14.5777 ⁽¹⁾	A	$ 13.98	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	11/08/2022		L		12.0515 ⁽¹⁾	A	$ 16.97	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	02/07/2023		L		11.9166 ⁽¹⁾	A	$ 17.21	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	05/09/2023		L		18.4285 ⁽¹⁾	A	$ 11.16	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/08/2023		L		12.9172 ⁽¹⁾	A	$ 15.99	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	11/07/2023		L		14.5225 ⁽¹⁾	A	$ 14.27	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	02/06/2024		L		15.4522 ⁽¹⁾	A	$ 13.46	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	05/06/2024		L		14.46 ⁽¹⁾	A	$ 14.43	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/05/2024		L		14.0955 ⁽¹⁾	A	$ 14.86	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	11/04/2024		L		15.6156 ⁽¹⁾	A	$ 16.15	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	02/10/2025		L		13.3087 ⁽¹⁾	A	$ 19.02	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	05/05/2025		L		15.5779 ⁽¹⁾	A	$ 16.3	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/04/2025		L		15.3405 ⁽¹⁾	A	$ 16.61	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	11/10/2025		L		16.2619 ⁽¹⁾	A	$ 18.35	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	02/09/2026		L		14.1217 ⁽¹⁾	A	$ 21.21	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	05/11/2026		L		14.3767 ⁽¹⁾	A	$ 20.9	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock	08/10/2026		L		11.8801 ⁽¹⁾	A	$ 25.38	4,319.6382 ⁽²⁾	D
Old Second Bancorp, Inc. Common Stock								15,430 ⁽³⁾	I	Living Trust
Restricted Stock Units								10,595	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. Represents shares acquired through the automatic reinvestment of cash dividends paid on shares of the Issuer's common stock held in the Reporting Person's individual retirement account, under a dividend reinvestment feature offered by the account custodian. The custodian's reinvestment feature is not a plan sponsored by the Issuer. These acquisitions were not previously reported because of an administrative oversight, and are reported herein to correct the omission.

2. The amount of securities beneficially owned represents the Reporting Person's holdings in her individual retirement account as of the date hereof, after giving effect to all dividend reinvestment transactions reported herein. The transactions reported herein were not previously reported.

3. The Reporting Person additionally beneficially owns 15,430 shares through her living trust as of October 15, 2026. This amount reflects her current trust holdings and supersedes the trust balance previously reported.

	/s/ Shirley Cantrell, Attorney-in-Fact	10/21/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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