Looking at the test suite, I see this test specifically aimed to check this:
(eval `(def-test-system test-defsystem-depends-on-4
Using git log test/test-defsystem-depends-on.script it looks like this is https://bugs.launchpad.net/asdf/+bug/1445638 Looking for that bug in git log, it was fixed in 3.1.4.5 on 2015-04-23.
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