diff --git a/software/SCSI2SD/src/geometry.c b/software/SCSI2SD/src/geometry.c
index 0666b5a..c3c6bb7 100755
--- a/software/SCSI2SD/src/geometry.c
+++ b/software/SCSI2SD/src/geometry.c
@@ -28,7 +28,16 @@ uint32_t getScsiCapacity(
 	uint32_t capacity =
 		(sdDev.capacity - sdSectorStart) /
 			SDSectorsPerSCSISector(bytesPerSector);
-	if (scsiSectors && (capacity > scsiSectors))
+
+	if (sdDev.capacity == 0)
+	{
+		capacity = 0;
+	}
+	else if (sdSectorStart >= sdDev.capacity)
+	{
+		capacity = 0;
+	}
+	else if (scsiSectors && (capacity > scsiSectors))
 	{
 		capacity = scsiSectors;
 	}
diff --git a/software/SCSI2SD/v4/SCSI2SD.cydsn/SCSI2SD.cyfit b/software/SCSI2SD/v4/SCSI2SD.cydsn/SCSI2SD.cyfit
index c2567cd..4ee1a97 100644
Binary files a/software/SCSI2SD/v4/SCSI2SD.cydsn/SCSI2SD.cyfit and b/software/SCSI2SD/v4/SCSI2SD.cydsn/SCSI2SD.cyfit differ