AMENDMENT NO. 2 TO SIXTH AMENDED AND RESTATED AGREEMENT OF LIMITED PARTNERSHIP OF CROSSTEX ENERGY, L.P.

Exhibit 3.1

AMENDMENT NO. 2 TO

SIXTH AMENDED AND RESTATED

AGREEMENT OF LIMITED PARTNERSHIP

OF

CROSSTEX ENERGY, L.P.

     This AMENDMENT NO. 2 TO SIXTH AMENDED AND RESTATED AGREEMENT OF LIMITED PARTNERSHIP OF CROSSTEX ENERGY, L.P. (this “Amendment No. 2”), is hereby adopted effective as of January 1, 2007 by Crosstex Energy GP, LLC, a Delaware limited liability company, the general partner of Crosstex Energy GP, L.P., a Delaware limited partnership (the “General Partner”), as general partner of Crosstex Energy, L.P., a Delaware limited partnership (the “Partnership”). Capitalized terms used but not defined herein are used as defined in the Sixth Amended and Restated Agreement of Limited Partnership of Crosstex Energy, L.P., dated as of March 23, 2007, as amended by Amendment No. 1 to the Sixth Amended and Restated Agreement of Limited Partnership, dated December 20, 2007 (the “Partnership Agreement”).

      WHEREAS , the General Partner and the Limited Partners of the Partnership entered into the Partnership Agreement; and

      WHEREAS , acting pursuant to the power and authority granted to it under Section 13.1(d) of the Partnership Agreement, the General Partner has determined that the following amendment to the Partnership Agreement does not require the approval of any Limited Partner;

      NOW THEREFORE , the General Partner does hereby amend the Partnership Agreement as follows:

     Section 1. Amendment .

     (a) Section 1.1 is hereby amended to add or amend and restate the following definitions:

     (i) “ Additional Book Basis ” means the portion of any remaining Carrying Value of an Adjusted Property that is attributable to positive adjustments made to such Carrying Value as a result of Book-Up Events. For purposes of determining the extent that Carrying Value constitutes Additional Book Basis:

(a) Any negative adjustment made to the Carrying Value of an Adjusted Property as a result of either a Book-Down Event or a Book-Up Event shall first be deemed to offset or decrease that portion of the Carrying Value of such Adjusted Property that is attributable to any prior positive adjustments made thereto pursuant to a Book-Up Event or Book-Down Event.

(b) If Carrying Value that constitutes Additional Book Basis is reduced as a result of a Book-Down Event and the Carrying Value of other property is increased as a result of such Book-Down Event, an allocable portion of any such increase in Carrying Value shall be treated as Additional Book Basis; provided , that the amount treated as Additional Book Basis pursuant hereto as a result of such Book-Down Event shall not exceed the amount by which the Aggregate Remaining Net Positive Adjustments after such Book-Down Event exceeds the remaining Additional Book Basis attributable to all of the Partnership’s Adjusted Property after such Book-Down Event (determined without regard to the application of this clause (b) to such Book-Down Event).

     (ii) “ Additional Book Basis Derivative Items ” means any Book Basis Derivative Items that are computed with reference to Additional Book Basis. To the extent that the Additional Book Basis attributable to all of the Partnership’s Adjusted Property as of the beginning of any taxable period exceeds the Aggregate Remaining Net Positive Adjustments as of the beginning of such period (the “ Excess Additional Book Basis ”), the Additional Book Basis Derivative Items for such period shall be reduced by the amount that bears the same ratio to the amount of Additional Book Basis Derivative Items determined without regard to this sentence as the Excess Additional Book Basis bears to the Additional Book Basis as of the beginning of such period.

     (iii) “ Adjusted Property ” means any property the Carrying Value of which has been adjusted pursuant to Section 5.5(d)(i) or 5.5(d)(ii).

     (iv) “ Aggregate Remaining Net Positive Adjustments ” means, as of the end of any taxable period, the sum of the Remaining Net Positive Adjustments of all the Partners.

     (v) “ Book Basis Derivative Items ” means any item of income, deduction, gain or loss included in the determination of Net Income or Net Loss that is computed with reference to the Carrying Value of an Adjusted Property (e.g., depreciation, depletion, or gain or loss with respect to an Adjusted Property).

     (vi) “ Disposed of Adjusted Property ” has the meaning assigned to such term in Section 6.1(d)(xi)(B).

     (vii) “ Net Positive Adjustments ” means, with respect to any Partner, the excess, if any, of the total positive adjustments over the total negative adjustments made to the Capital Account of such Partner pursuant to Book-Up Events and Book-Down Events.

     (viii) “ Net Termination Gain ” means, for any taxable year, the sum, if positive, of all items of income, gain, loss or deduction recognized by the Partnership (a) after the Liquidation Date or (b) upon the sale, exchange or other

disposition of all or substantially all of the assets of the Partnership Group, taken as a whole, in a single transaction or a series of related transactions (excluding any disposition to a member of the Partnership Group). The items included in the determination of Net Termination Gain shall be determined in accordance with Section 5.5(b) and shall not include any items of income, gain or loss specially allocated under Section 6.1(d).

     (ix) “ Net Termination Loss ” means, for any taxable year, the sum, if negative, of all items of income, gain, loss or deduction recognized by the Partnership (a) after the Liquidation Date or (b) upon the sale, exchange or other disposition of all or substantially all of the assets of the Partnership Group, taken as a whole, in a single transaction or a series of related transactions (excluding any disposition to a member of the Partnership Group). The items included in the determination of Net Termination Loss shall be determined in accordance with Section 5.5(b) and shall not include any items of income, gain or loss specially allocated under Section 6.1(d).

     (x) “ Remaining Net Positive Adjustments ” means as of the end of any taxable period, (i) with respect to the Unitholders holding Common Units, Subordinated Units, Senior Subordinated Series C Units or Senior Subordinated Series D Units, the excess of (a) the Net Positive Adjustments of the Unitholders holding Common Units, Subordinated Units, Senior Subordinated Series C Units or Senior Subordinated Series D Units as of the end of such period over (b) the sum of those Partners’ Share of Additional Book Basis Derivative Ite