https://en.wikipedia.org/w/index.php?title=Special%3APrefixIndex&prefix=A&namespace=0
There are way more pages starting with A than listed there (E.g. ABBA, Apple).
Also affects empty queries, e.g. https://az.wikipedia.org/w/index.php?title=X%C3%BCsusi%3APrefixIndex&prefix=A&namespace=8 does not list Monobook.js but stops at Gadget-*.