Wrong number of modifier arguments in nested custom modifiers

[Defelo]

The following code used to work fine on 0.3.1 but now fails on 0.4.0 with the error below:

A! ← ^1
B! ← A!^1

B!(×7) 6

Error: The name B! implies 1 modifier arguments, but the binding body references 2. Try `B!!`.
  at test.ua:2:1
2 | B! ← A!^1
    ──

A quick git bisect revealed that this bug was introduced by commit ffe7e06 (at least I assume this is as bug since it worked before and I couldn't find anything about this neither in the latest change log nor in the documentation).