citext function overloads for text parameters

test=# select strpos('Aa'::citext, 'a');

 strpos 

--------

      1

However, if I pass a typed text parameter for the substring, I get case-sensitive behavior instead:

test=# select strpos('Aa'::citext, 'a'::text);

 strpos 

--------

      2

This seems like surprising behavior - my expectation was that the first parameter being citext would be enough to trigger case-insensitive behavior. The same may be happening with other string functions (e.g. regexp_matches). This is causing some difficulties in a real scenario where SQL and parameters are getting generated by an O/RM, and changing them isn't trivial.

Do the above seem like problematic behavior like it does to me, or is it the expected behavior?