Error when using filterxt links for thread prefixes, after updating to MyBB 1.8.6

[Shane777]

I recently upgraded my board to MyBB 1.8.6.  Everything with XThreads seems to work fine except for some prefix filter links I have on one of my forums.  Here is the error I get when clicking those links:

SQL Error:
1054 - Unknown column 'prefix' in 'where clause'
Query:
SELECT DISTINCT tid,uid FROM mybb_posts WHERE uid='1' AND tid IN (21896,21883,21747,21742,21719,21673,21672,21630,21614,21587,21556,21429,21425,21373,21362,21332,212​88,21284,21059,20997,20842,20840,20744,20357,20241,15365,13707) AND visible IN (-1,0,1) AND `prefix` IN (5)


An example of one of the links that causes that error to appear is this link:
/forumdisplay.php?fid=18&filterxt_prefix=5

The error only happens while logged in.  For some reason, if I'm viewing as a guest, the links work correctly.

Before updating to MyBB 1.8.6, they all worked perfectly.  After I upgraded to MyBB 1.8.6, I also made sure to upgrade XThreads yesterday just to see if that would help.  The error remained even after updating XThreads.

How can I fix this?  I am comfortable editing core files if you have some find/replace instructions I can follow.  Thanks.