Exhibit 10.1

AMENDMENT NO. 18

TO

AMENDED AND RESTATED

LIMITED PARTNERSHIP AGREEMENT

OF

FIRST POTOMAC REALTY INVESTMENT LIMITED PARTNERSHIP

This Amendment No. 18 to the Amended and Restated Limited Partnership Agreement
of First Potomac Realty Investment Limited Partnership (this “Amendment”) is
made as of March 14, 2012 by First Potomac Realty Trust, a Maryland real estate
investment trust, as sole general partner (the “Company”) of First Potomac
Realty Investment Limited Partnership, a Delaware limited partnership (the
“Partnership”), pursuant to the authority granted to the Company in the Amended
and Restated Limited Partnership Agreement of First Potomac Realty Investment
Limited Partnership, dated as of September 15, 2003, as amended (the
“Partnership Agreement”), for the purpose of issuing additional Series A
Preferred Partnership Units to the Company in its capacity as the General
Partner. Capitalized terms used and not defined herein shall have the meanings
set forth in the Partnership Agreement.

WHEREAS, a pricing committee of the Board of Trustees (the “Board”) of the
Company adopted resolutions on January 12, 2011 classifying and designating
4,600,000 Preferred Shares (as defined in the First Amended and Restated
Declaration of Trust of the Company (the “Declaration of Trust”)) as Series A
Preferred Shares;

WHEREAS, the Company filed Articles Supplementary to the Declaration of Trust
with the State Department of Assessments and Taxation of Maryland (the “MSDAT”),
effective on January 18, 2011 (the “Original Articles Supplementary”),
establishing the Series A Preferred Shares, with such preferences, rights,
powers, restrictions, limitations as to distributions, qualifications and terms
and conditions of redemption as described in the Original Articles
Supplementary, and classifying and establishing 4,600,000 Preferred Shares (as
defined in the Declaration of Trust) as Series A Preferred Shares;

WHEREAS, on January 18, 2011, the Company amended the Partnership Agreement to
create Partnership Units in the form of Series A Preferred Partnership Units
having designations, preferences and other rights which are substantially the
same as the economic rights of the Series A Preferred Shares, and classifying
and designating 4,600,000 Partnership Units as Series A Preferred Partnership
Units;

WHEREAS, on January 18, 2011, the Company issued 4,000,000 Series A Preferred
Shares, and, on January 28, 2011, the Company issued an additional 600,000
Series A Preferred Shares in connection with the exercise of the underwriters’
overallotment option;

WHEREAS, a pricing committee of the Board adopted resolutions on March 9, 2012
classifying and designating an additional 1,800,000 Preferred Shares (as defined
in the Declaration of Trust) as Series A Preferred Shares;

WHEREAS, on March 12, 2012, the Company filed Articles Supplementary to the
Declaration of Trust with the MSDAT, effective on March 14, 2012, classifying
and designating an additional 1,800,000 Preferred Shares (as defined in the
Declaration of Trust) as Series A Preferred Shares;

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WHEREAS, on March 14, 2012, the Company issued an additional 1,800,000 Series A
Preferred Shares; and

WHEREAS, the Company has determined in good faith that (i) in connection with
the issuance of the additional Series A Preferred Shares, it is necessary and
desirable to amend the Partnership Agreement to classify and designate
additional Partnership Units as Series A Preferred Partnership Units, and
(ii) the issuance of the additional Series A Preferred Partnership Units to the
General Partner is in the best interests of the Company and the Partnership.

NOW, THEREFORE, in consideration of the premises and for other good and valuable
consideration, the receipt and sufficiency of which hereby are acknowledged, the
Partnership Agreement is hereby amended as follows:

1. Exhibit E to the Partnership Agreement is hereby amended by deleting Section
A thereof and replacing such Section with the following new Section A:

“A. Designation and Number. A series of Preferred Partnership Units, designated
as Series A Preferred Partnership Units, is hereby established. The number of
Series A Preferred Partnership Units shall be 6,400,000.”

2. In accordance with Section 4.02 of the Partnership Agreement, set forth in
Exhibit E, as amended hereby, are the terms and conditions of the additional
Series A Preferred Partnership Units hereby established and issued to the
Company in consideration of its contribution to the Partnership of the proceeds
of the issuance and sale of the additional Series A Preferred Shares by the
Company. The books and records of the Partnership shall be revised to reflect
the issuance of the additional Series A Preferred Partnership Units.

3. Except as modified herein, all terms and conditions of the Partnership
Agreement shall remain in full force and effect, which terms and conditions the
Company hereby ratifies and confirms.

4. This Amendment shall be construed and enforced in accordance with and
governed by the laws of the State of Delaware, without regard to conflicts of
law.

5. If any provision of this Amendment is or becomes invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions contained herein shall not be affected thereby.

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IN WITNESS WHEREOF, the undersigned has executed this Amendment as of the date
first set forth above.

 

FIRST POTOMAC REALTY TRUST

As sole general partner of First Potomac Realty Investment Limited Partnership

By:   /s/  Barry H. Bass Name:     Barry H. Bass Title:   EVP, CFO

[Signature Page to Amendment No. 18 to the Amended and Restated Limited
Partnership Agreement of First Potomac Realty Investment Limited Partnership]