The 22-year-old Australian striker, who joined the Spireites on loan on Friday, was expected today to make the move permanent.
But assistant manager Lee Richardson said: "I think that McMaster signing until the end of the season is a possibility.
"We know all about Jamie and it has been a question of timing. We now have him on loan and he needs to play games.
"Jamie needs to play first-team football and needs time to settle in somewhere, so we will be looking at that."