Old Second Bancorp corrects Klaeser’s share settlement

The amendment clarifies that the 3,077-unit vesting settlement involved no shares sold or withheld for taxes.

This filing corrects an earlier one, and you can read the original Form 4 if you want to see what changed.

Rhea-AI Filing Summary

Old Second Bancorp Inc. (OSBC) director Dennis L. Klaeser settled 3,077 restricted stock units upon vesting into an equal number of common shares on February 21, 2026. After the transaction, his reported direct holdings were 10,595 restricted stock units and 7,657 common shares. The amendment corrects the original Form 4, which used transaction code F for the settlement; the footnote states that no shares were sold or withheld to satisfy taxes.

Insider Trade Summary

Other: 6,154 shares

Other 2 txns

Insider KLAESER DENNIS L

Role Director

Type	Security	Shares	Price	Value
Other	Restricted Stock Units F1	3,077	$0.00	$0.00
Other	Old Second Bancorp, Inc. Common Stock F1	3,077	$0.00	$0.00

Holdings After Transaction: Restricted Stock Units — 10,595 shares (Direct); Old Second Bancorp, Inc. Common Stock — 7,657 shares (Direct)

Footnotes (1)

1. F1. Represents the settlement upon vesting of 3,077 restricted stock units into an equal number of shares of common stock. No shares were sold or withheld to satisfy taxes. This amendment corrects the original Form 4, which incorrectly reported the settlement using transaction code F.

Key Figures

Restricted stock units settled: 3,077 restricted stock units Common shares received: 3,077 common shares Restricted stock units held after transaction: 10,595 restricted stock units +1 more

4 metrics

Restricted stock units settled 3,077 restricted stock units Settled upon vesting on February 21, 2026

Common shares received 3,077 common shares Received upon settlement on February 21, 2026

Restricted stock units held after transaction 10,595 restricted stock units Reported following the transaction on February 21, 2026

Common shares held after transaction 7,657 common shares Reported following the transaction on February 21, 2026

Key Terms

Restricted Stock Units, settlement upon vesting, transaction code F

3 terms

Restricted Stock Units financial

"settlement upon vesting of 3,077 restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

settlement upon vesting financial

"Represents the settlement upon vesting"

transaction code F technical

"incorrectly reported the settlement using transaction code F"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many OSBC shares did director Dennis L. Klaeser receive?

Dennis L. Klaeser received 3,077 common shares when 3,077 restricted stock units settled upon vesting on February 21, 2026. Following the transaction, his reported direct holdings included 7,657 common shares and 10,595 restricted stock units.

What did OSBC Form 4/A correct?

The amendment corrected the original Form 4, which incorrectly reported the settlement using transaction code F. The footnote states that no shares were sold or withheld to satisfy taxes.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/20/2026 - 01:42 PM EDT Accepted by SEC EDGAR 10/20/2026 - 01:42 PM EDT Learn about SEC filing dates

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

KLAESER DENNIS L

(Last) (First) (Middle)

37 S. RIVER ST.

(Street)

AURORA ILLINOIS 60506

(City) (State) (Zip)

UNITED STATES

(Country)

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)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
02/21/2026

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

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

4. If Amendment, Date of Original Filed (Month/Day/Year)
02/25/2026

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)
			Code	V	Amount	(A) or (D)	Price
Restricted Stock Units	02/21/2026		J		3,077(1)	D	$0	10,595	D
Old Second Bancorp, Inc. Common Stock	02/21/2026		J		3,077(1)	A	$0	7,657	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents the settlement upon vesting of 3,077 restricted stock units into an equal number of shares of common stock. No shares were sold or withheld to satisfy taxes. This amendment corrects the original Form 4, which incorrectly reported the settlement using transaction code F.

	/s/ Shirley Cantrell, Attorney-in-Fact	10/20/2026
	** 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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)