Glue not supported

[surpavan]

Firstly, thank you for the wonderful package, work life is made easy with it.

When using glue() function in subject, it is not supporting, it is throwing below error:

Error in FUN(X[[i]], ...) : 
  Sorry, parameter type `NA' is ambiguous or not supported.

If I remove glue or wrap it in paste() it works.

library(glue)

send.mail(from='an email address',
          to=c('some email'),
          subject=paste(glue("test- {strftime(startdate,'%B %Y')}")),
          body=content_html,
          html=TRUE,
          smtp=list(host.name='something here',send=TRUE),
          authenticate = FALSE,
          attach.files = currentpath)