diff --git a/lib/ac-api/src/main/java/com/webcodepro/applecommander/storage/os/dos33/DosFormatDisk.java b/lib/ac-api/src/main/java/com/webcodepro/applecommander/storage/os/dos33/DosFormatDisk.java
index 459d5986..e4f374ea 100644
--- a/lib/ac-api/src/main/java/com/webcodepro/applecommander/storage/os/dos33/DosFormatDisk.java
+++ b/lib/ac-api/src/main/java/com/webcodepro/applecommander/storage/os/dos33/DosFormatDisk.java
@@ -732,7 +732,7 @@ public class DosFormatDisk extends FormattedDisk {
 	 */
 	protected int getFreeMapByte(int track, int sector) {
 		int trackOffset = track * 4;
-		int sectorOffset = 1 - ((sector & 0x8) >> 3);
+		int sectorOffset = (device.getGeometry().sectorsPerTrack() - sector - 1) >> 3;
 		return 0x38 + trackOffset + sectorOffset;
 	}