diff --git a/src/hnswbuild.c b/src/hnswbuild.c
index 73ec72b..382f2a4 100644
--- a/src/hnswbuild.c
+++ b/src/hnswbuild.c
@@ -1148,6 +1148,8 @@ RecordFreeSpace(Relation index)
 		blkno = HnswPageGetOpaque(page)->nextblkno;
 		UnlockReleaseBuffer(buf);
 	}
+
+	FreeSpaceMapVacuum(index);
 }
 
 /*