Liam Smith has extended his Hearts contract until 2019 and joined St Mirren on loan until next summer.
The 21-year-old defender heads to Paisley to augment his first-team experiences in the Championship after 38 senior appearances in maroon.
He remains highly regarded by Riccarton coaching staff, hence the deal to extend his contract by 12 months. Smith's existing deal was due to expire next summer but he is now tied to Tynecastle until 2019.
The arrival of Northern Ireland internationalist Michael Smith, plus the emergence of teenager Jamie Brandon, would have left Smith with limited game time this season. He is expected to play regularly at St Mirren under the former Hearts coach Jack Ross.