Memory exceeded with str.substr in 4.8.13

[icemonster]

This query:

(declare-const str1 String)
(assert (not (= (str.substr str1 1 999999) "someString")))
(check-sat)

immediately returns sat when using Z3 4.8.7. However, when using 4.8.13 (or 4.8.11, haven't tried more versions) it fills up the RAM, or if we give it enough memory (~10GB) it takes forever.

I use that big upper bound 999999 as a way to represent the "end of the string" str1.