Sonko's position as Nairobi County boss is in jeopardy following today's court ruling.
On Thursday, Sonko lost a bid for the petition challenging his victory to be struck out.
High Court judge Msagha Mbogholi in his ruling dismissed Sonko's argument saying it was not mandatory for the petitioners to list Deputy Governor Polycarp Igathe as a respondent in the case.
Sonko had earlier requested the court to struck out the petition challenging his August win through his lawyers Harrison Kinyanjui and Cecil Miller.
The Governor's lawyers had argued his election could not be separated from that of his deputy.
The ruling comes after the Independent Electoral and Boundaries Commission (IEBC) and two voters made their final submissions on Monday.
The two petitioners, Japeth Muroko and Zacheus Okoth Oliech, opposed Sonko’s argument claiming that his application lacked merit.
They insisted their argue that their petition was within the confines of the law under the mandatory provisions of rule 8 of the Elections (County and Parliamentary petitions) rules.
The two petitioners argued that Igathe was not an elective candidate in the gubernatorial elections since he was not nominated by any political party as a candidate.
Last month, the High Court thwarted former Nairobi Governor Evans Kidero's bid to be enjoined in the same petition seeking to annul the election Sonko.
Dr Kidero sought to be enjoined in the case filed by Muroko and Oliech as an interested party.