Connor Dixon joined the Celts on loan from Derby County prior to the registration deadline in March.
The 22-year-old midfielder signed professional terms with the Rams in 2019, and became a regular for their Under 23s side, making 15 appearances and scoring twice in Premier League 2 – Division 1 last season.
Dixon spent the early part of this season recovering from injury, but has been out on loan at Southern League Premier Division Central side Ilkeston Town since early February.