Using dllmap on monomac

Using dllmap on monomac

I'm trying to use a custom build of sqlite with MonoMac, effectively as
per this question.
However, using dllmap doesn't seem to be working.
My custom dylib is being deployed into
[myapp.app]/Contents/Frameworks/mycustomlib.dylib
Output of otool -L mycustomlib.dylib looks correct:
@executable_path/../Frameworks/mycustomlib.dylib (compatibility version
0.0.0, current version 0.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version
169.3.0)
My myapp.exe.config file looks like this:
<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
<dllmap dll="sqlite3"
target="@executable_path/../Frameworks/mycustomlib.dylib"
os="!windows" />
</configuration>
And I have verified that it is being copied alongside myapp.exe in
[MyApp.app]/Contents/MonoBundle.
I can force this to work by recompiling Mono.Data.Sqlite and directly
replacing the reference to sqlite3 with mycustomlib. However, the dllmap
route is much nicer.
What am I missing? How can I debug this?