Repeatable 404 on particular search requests

[plwww]

When making search endpoint requests, I notice some requests repeatedly failing. It seems to happen only on searches for tracks with long names. As an example: the following fails:

  https://api.spotify.com/v1/search/?type=track&q=I%20Slept%20With%20Someone%20In%20Fall%20Out%20Boy%2...

I notice if I cut it down till there's only a total of 20 space-delimited terms, it works. For example, the following works:

   https://api.spotify.com/v1/search/?type=track&q=I%20Slept%20With%20Someone%20In%20Fall%20Out%20Boy%2...

Other searches have seen the same results, 404 until I drop below 20 terms. I haven't found  any documentation stating there's such a limit, and if the search endpoint is capped at 20 I would expect to get perhaps a 400 error rather than a 404. Is there any documentation that covers this, or is it a bug?