[SCHEDULE 13D/A] MIDDLEFIELD BANC CORP Amended Major Shareholder Report

Rhea-AI Filing Summary

Middlefield Banc Corp. common stock ownership shifted as Castle Creek reduced its stake. Castle Creek Capital Partners VI, LP sold 247,653 shares of Voting Common Stock between December 12, 2025 and February 2, 2026 for proceeds of $8,546,310.15 in open-market transactions.

After these sales, the fund owns 312,847 shares, or about 3.9% of Middlefield Banc's 8,090,067 Voting Common shares outstanding as of December 12, 2025. As of February 2, 2026, the reporting persons ceased to be beneficial owners of more than five percent of the company's Voting Common Stock.

Insights

Equity ownership and activism analyst

Castle Creek sold stock and dropped below the 5% ownership threshold in Middlefield Banc.

The filing shows Castle Creek Capital Partners VI, LP sold 247,653 shares of Middlefield Banc Corp. Voting Common Stock for $8,546,310.15 in open-market, broker-assisted trades between December 12, 2025 and February 2, 2026. Remaining holdings are 312,847 shares.

Those 312,847 shares represent about 3.9% of 8,090,067 shares outstanding as of December 12, 2025. The filing states that, as of February 2, 2026, the reporting persons are no longer beneficial owners of more than five percent, meaning they have moved below a key disclosure and influence threshold under U.S. securities rules.

Castle Creek and its managing entity, Castle Creek Capital VI LLC, report shared voting and dispositive power over these shares, while the LLC disclaims beneficial ownership beyond its pecuniary interest. Future ownership changes, if material, would be reflected in subsequent beneficial ownership reports.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

MIDDLEFIELD BANC CORP.

(Name of Issuer)

Common Stock, no par value

(Title of Class of Securities)

596304204

(CUSIP Number)

Deborah Sykes
11682 El Camino Real, Suite 320,
San Diego, CA, 92130
858-756-8300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

01/30/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 596304204

1

Name of reporting person

Castle Creek Capital Partners VI, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 312,847.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 312,847.00

11

Aggregate amount beneficially owned by each reporting person

312,847.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

3.9 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

(1) The information set forth in Item 5 of this statement on Schedule 13D is incorporated herein by reference.

SCHEDULE 13D

CUSIP No. 596304204

1

Name of reporting person

Castle Creek Capital VI LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF, WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 312,847.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 312,847.00

11

Aggregate amount beneficially owned by each reporting person

312,847.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

3.9 %

14

Type of Reporting Person (See Instructions)

HC, OO

Comment for Type of Reporting Person:

(1) The information set forth in Item 5 of this statement on Schedule 13D is incorporated herein by reference.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, no par value
(b)	Name of Issuer: MIDDLEFIELD BANC CORP.
(c)	Address of Issuer's Principal Executive Offices: 15985 East High Street, Middlefield, OHIO , 44062.
Item 1 Comment: This Amendment No. 1 to Schedule 13D (this "Amendment No. 1") amends and supplements the Schedule 13D filed on December 9, 2022 (the "Schedule 13D") with the U.S. Securities and Exchange Commission (the "SEC"), relating to the shares of common stock, no par value per share ("Voting Common Stock"), of Middlefield Banc Corp. (the "Issuer" or the "Company"). Unless specifically amended hereby, the disclosures set forth in the Schedule 13D remain unchanged. Capitalized terms used in this Amendment No. 1 that are not otherwise defined herein have the meanings attributed to them in the Schedule 13D.
Item 3.	Source and Amount of Funds or Other Consideration
	Item 3 of the Schedule 13D is hereby amended and supplemented by adding the following: Between December 12, 2025 and February 2, 2026 (inclusive), Castle Creek Capital Partners VI, LP ("Fund VI") sold an aggregate of 247,653 shares of Voting Common Stock for proceeds of $8,546,310.15, which represents an amount net of commissions and fees, in various open-market transactions. Following such transactions, Fund VI owns 312,847 shares of Voting Common Stock.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5(a) and (b) of the Schedule 13D is hereby amended and supplemented as follows: Fund VI owns 312,847 shares of the Voting Common Stock, which represents approximately 3.9%* of the Voting Common Stock. *This calculation is based on 8,090,067 shares of Voting Common Stock of the Company outstanding as of December 12, 2025, as reported in the Company's proxy statement on Schedule 14A filed with the SEC on December 19, 2025.
(b)	Fund VI has shared power to vote or direct the vote and shared power to dispose or direct the disposition of the 312,847 shares of Voting Common Stock described above with CCC VI. CCC VI disclaims beneficial ownership of the Voting Common Stock beneficially owned by Fund VI, except to the extent of its pecuniary interest therein.
(c)	Item 5(c) of the Schedule 13D is hereby amended and supplemented as follows: Except as previously disclosed in the Schedule 13D, Fund VI has engaged in the following open market, broker-assisted transactions with respect to the Voting Common Stock during the last 60 days through the date of the event which requires filing of this Schedule 13D: (i) 16,813 shares of Voting Common Stock sold on December 12, 2025 at a weighted average price of $37.17 per share (in multiple open market, broker-assisted transactions ranging from $36.90 to $37.25 per share, inclusive); (ii) 13,579 shares of Voting Common Stock sold on December 15, 2025 at a weighted average price of $37.00 per share (in multiple open market, broker-assisted transactions ranging from $37.00 to $37.18 per share, inclusive); (iii) 5,627 shares of Voting Common Stock sold on December 16, 2025 at a weighted average price of $37.01 per share (in multiple open market, broker-assisted transactions ranging from $37.00 to $37.095 per share, inclusive); (iv) 5,302 shares of Voting Common Stock sold on December 17, 2025 at a weighted average price of $37.12 per share (in multiple open market, broker-assisted transactions ranging from $37.00 to $37.20 per share, inclusive); (v) 12,909 shares of Voting Common Stock sold on December 18, 2025 at a weighted average price of $37.04 per share (in multiple open market, broker-assisted transactions ranging from $36.90 to $37.27 per share, inclusive); (vi) 200 shares of Voting Common Stock sold on December 19, 2025 at a price of $36.90 per share; (vii) 18,008 shares of Voting Common Stock sold on January 22, 2026 at a weighted average price of $36.12 per share (in multiple open market, broker-assisted transactions ranging from $36.00 to $36.505 per share, inclusive); (viii) 72,772 shares of Voting Common Stock sold on January 30, 2026 at a weighted average price of $33.57 per share (in multiple open market, broker-assisted transactions ranging from $33.50 to $33.79 per share, inclusive); and (ix) 102,443 shares of Voting Common Stock sold on February 2, 2026 at a weighted average price of $33.61 per share (in multiple open market, broker-assisted transactions ranging from $33.30 to $33.98 per share, inclusive).
(e)	As of February 2, 2026, the Reporting Persons ceased to be the beneficial owner of more than five percent of the Voting Common Stock.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Castle Creek Capital Partners VI, LP

Signature:	/s/ Tony Scavuzzo
Name/Title:	Tony Scavuzzo, Managing Principal
Date:	02/03/2026

Castle Creek Capital VI LLC

Signature:	/s/ Tony Scavuzzo
Name/Title:	Tony Scavuzzo, Managing Principal
Date:	02/03/2026