THIRD AMENDMENT TO SECOND AMENDED AND RESTATED LIMITED PARTNERSHIP AGREEMENT OF CORPORATE OFFICE PROPERTIES, L.P. THIS THIRD AMENDMENT (the "Amendment") to the Second Amended and Restated Limited Partnership Agreement of Corporate Office Properties, L.P., a Delaware limited partnership (the "Partnership") is made and entered into as of September 29, 2000 by and among the undersigned parties. RECITALS A. The Partnership is a limited partnership organized under the Delaware Revised Uniform Limited Partnership Act and governed by that certain Second Amended and Restated Limited Partnership Agreement dated as of December 7, 1999, as amended by that certain First Amendment to Second Amended and Restated Limited Partnership Agreement dated December 21, 1999 and by that certain Second Amendment to Second Amended and Restated Limited Partnership Agreement dated December 21, 1999 (as amended, the "Partnership Agreement"). B. The sole general partner of the Partnership is Corporate Office Properties Trust, a real estate investment trust formed under the laws of the State of Maryland (the "General Partner"). C. The Partnership has entered into a certain Warrant Exchange Agreement (the "Exchange Agreement") dated as of September 29, 2000 with United Properties Group, Incorporated, a New York corporation ("UPG"). D. As required under Sections 2 and 3.1 of the Exchange Agreement, UPG intends to transfer its interest in a certain warrant to purchase common units in the Partnership (the "Warrant") to the Partnership in exchange for partnership interests in the Partnership having designations, rights and preferences as set forth in Section 5 of the Exchange Agreement (the "Series C Preferred Units"). E. The parties desire to amend the Partnership Agreement to provide for the contribution of the Warrant by UPG to the Partnership in exchange for the Series C Preferred Units in accordance with Section 3.1 of the Exchange Agreement. Unless otherwise defined herein, all capitalized terms used in this Amendment shall have the same meanings as set forth in the Partnership Agreement. NOW THEREFORE, in consideration of the foregoing and of the mutual premises set forth herein, the parties hereto, intending to be legally bound hereby, hereby amend the Partnership Agreement as follows, effective as of the date set forth above. 1. The foregoing recitals to this Amendment are hereby incorporated in and made a part of this Amendment. 2. (a) Upon closing of the Exchange Agreement, UPG shall contribute the Warrant to the Partnership. (b) Upon the contribution of the Warrant to the Partnership by UPG, and in accordance with Section 3.1 of the Exchange Agreement, the Partnership shall issue to UPG 42,000 Series C Preferred Units, which Preferred Units shall constitute Senior Preferred Units. (c) For purposes of the Partnership Agreement, including the maintenance of Capital Accounts, UPG shall be treated as making a Capital Contribution of $1,050,000. (d) The General Partner shall amend Exhibit 1 to the Partnership Agreement by adding the Addendum to Exhibit 1 in the form attached hereto to reflect the issuance of the Series C Preferred Units to UPG and the General Partner hereby confirms certain rights attendant thereto, including, without limitation, the rights to the Liquidation Preference and the Priority Return Percentage set forth therein, and the right to convert such Preferred Units into Partnership Units at the Conversion Factor set forth therein. The Conversion Factor for the Series C Preferred Units shall be entitled to the same anti-dilution protection applicable to the other Preferred Units previously issued to UPG. 3. This Amendment shall take effect upon the closing of the transactions contemplated by the Exchange Agreement, including without limitation the contribution of the Warrant to the Partnership by UPG, and in the event such closing does not occur, this Amendment shall be of no force or effect. (REMAINDER OF PAGE INTENTIONALLY LEFT BLANK) 2 In witness whereof, the parties hereto have caused their duly authorized representatives to execute this Amendment as of the day and year first above written. UNITED PROPERTIES GROUP, INCORPORATED, a New York corporation By: /s/ JOSEPH S. THOMPSON ---------------------------- Name: Joseph S. Thompson Its: Vice President CORPORATE OFFICE PROPERTIES TRUST, a Maryland Real Estate Investment Trust By: /s/ ROGER A. WAESCHE, JR. ------------------------------- Name: Roger A. Waesche, Jr. Its: Senior Vice President and Chief Financial Officer 3 Exhibit 1 SCHEDULE OF PARTNERS