**EXHIBIT 10.4****ADDENDUM TO STOCK OPTION AGREEMENT**     This Addendum (the “Addendum”) to the Stock Option Agreement (the “OptionAgreement”) pursuant to the Keynote Systems, Inc. **1999 Equity Incentive Plan**by and between**Eric Stokesberry**(the “Optionee”) and Keynote Systems, Inc. (the “Company”) isentered into by and between Optionee and the Company as of **April 4, 2006**.**WITNESSETH**WHEREAS, the Optionee is an officer of the Company; andWHEREAS, the Company, as a matter of practice, provides for the acceleration, in certain cases, ofthe vesting of options (“Options”) granted to its officers;NOW, THEREFORE, THE PARTIES HEREBY AGREE AS FOLLOWS:1. The Company and the Optionee are entering into this Addendum to the Option Agreement,concurrently with the execution of the Option Agreement, in order to specify the terms andconditions of the acceleration, in certain cases, of the vesting of Options granted to the Optioneeunder the Option Agreement.2. The following language shall be included at the end of 2.1 of the Option Agreement:   “Notwithstanding the provisions of the preceding sentence regarding the rate at which thisOption shall vest, in the event that upon or after a Sale of the Company, Optionee’semployment with the Company, or its successor, is terminated without Cause, within twelvemonths from the Sale of the Company, then immediately prior to the effectiveness of suchtermination this Option shall vest with respect to (i) 25% of the Shares, if the date oftermination is less than one year from date of grant or (ii) 100% of the Shares, if the dateof termination is more than one year from date of grant. For such purposes, the term “Saleof the Company” means any sale or disposition of all or substantially all of the assets ofthe Company, or any merger or consolidation of the Company with or into any othercorporation, corporations, or other entity in which more than 50% of the Company’s votingpower is transferred. The term “Cause” means (i) willfully engaging in gross misconductthat is materially and demonstrably injurious to the Company; (ii) willful and continuedfailure to substantially perform Optionee’s duties with the Company (other than incapacitydue to physical or mental illness), provided that such failure continues after the Board ofDirectors has provided Optionee with a written demand for substantial performance, settingforth in detail the specific respects in which it believes Optionee has willfully and notsubstantially performed his duties thereof and a reasonable opportunity (to be not less than30 days) to cure the same. For the above purposes, a termination by the Company withoutCause includes a termination of employment by Optioneewithin 30 days following any one of the following events: (x) a 10% or more reduction inOptionee’s salary that is not part of a general salary reduction 
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  plan applicable to allofficers of the successor Company; (y) a change in Optionee’s position or status to aposition that is not at the level of Vice President or above with the successor; or (z)relocating Optionee’s principal place of business, in excess of fifty (50) miles from thecurrent location of such principal place of business. This Option shall cease to vest uponOptionee’s Termination and Optionee shall in no event be entitled under this Option topurchase a number of shares of the Company’s Common Stock greater than the “Total OptionShares.”**[The remainder of this page is intentionally left blank.]**
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     **IN WITNESS WHEREOF**, the Company has caused this Agreement to be executed in duplicate by itsduly authorized representative and Optionee has executed this Agreement in duplicate as of the datefirst specified above.         **KEYNOTE SYSTEMS INC.**   **OPTIONEE**           By: \s\ Umang Gupta    \s\ Eric Stokesberry (Signature)           Umang Gupta   Eric Stokesberry         (Please print name)   (Please print name)           CEO             (Please print title)      
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