Boundary Event Signal does not translate variables while registring as Signal Event Listener

Define a process with a subprocess inside it. The process has a variable with name document-ref. Initialize the variable with value: 123 The subprocess fires a terminate event with signal ref 'document-approved-# {signal-ref}' Attach to this subprocess boundary a Signal Event with signalRef defined as before and perform something from this capture event. Despite de subprocess fires properly the signal with signalRef 'document-approved-123', The boundary Signal capture has registered itself to listen 'document-approved-#{signal-ref} ' inspite of 'document-approved-123' The signal is never captured.