Should I sign a new confidentiality agreement with my primary client.

I am a freelance graphic designer and have been (up til now) been categorized by my client as an independent contractor. Now, because I am working more often and usually on-site, they want to change my status to "casual employee", and file a W2 for me, rather than a 1099. This is fine, except for the rather broadly worded "exclusive services" section of the new agreement. I quote: "Competing business enterprise means any business that provides advertising, marketing or sales consulting services, designs, printing and/or manufactured displays." They are aware I have other clients. They are also not agreeing to keep me on retainer, or guarantee a minimum amount of work per week, but will continue to call me on an "as needed" basis.
Am I correct in asking for a rewording, etc?