Variable content as "Value" in util:RegistrySearch

[ManuHArt]

I'm converting a bootstrapper with multiple MSIs from 3.12 to WiX 4.0.4.

During this migration I found out that using the contents of a variable as "Value" in RegistrySearch from the Utils extension does not work anymore :

<Variable Name="SqlInstance" Value="MyProductSql" Persisted="yes" Type="formatted" />
      
<util:RegistrySearch Id="SqlInstanceFound"
                     Root="HKLM"
                     Key="SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL"
                     Value="[SqlInstance]"
                     Result="exists"
                     Variable="DefaultSqlInstanceFound" />

In WiX 3.12, this yielded the following log message:
[0B64:03A0][2024-03-11T16:32:47]i000: Registry value not found. Key = 'SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL', Value = 'MyProductSql'

In WiX 4.0.4 however, the following message is logged:
[0B64:03A0][2024-03-11T16:32:47]i000: Registry value not found. Key = 'SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL', Value = '[SqlInstance]'

How do I have to define the RegistrySearch?
I didn't find any mentioning in the documentation of such a change in behavior.