There Needs to Be Enough Subject-Verb Agreement

In my previous blog entry I said:

so there need to be enough serviceable customers locally to sustain you

I initially wrote:

so there needs to be enough serviceable customers locally to sustain you

but I decided that "need" has to agree with "serviceable customers".

I confess, though, that I struggled for a while with it (although, as with many cases like this, it's clear to me now that I've thought about it).