California Code, Code of Civil Procedure - CCP § 410.42

(a) The following provisions of a contract between the contractor and a subcontractor with principal offices in this state, for the construction of a public or private work of improvement in this state, shall be void and unenforceable:

(b) For purposes of this section, “construction” means any work or services performed on, or materials provided for, a work of improvement, as defined in Section 8050 of the Civil Code, and for which a lien may be claimed pursuant to Section 8400 of the Civil Code (whether or not a lien is in fact claimed) or for which such a lien could be claimed but for Section 8160 of the Civil Code.