diff -up parted-1.9.0/libparted/arch/linux.c.orig parted-1.9.0/libparted/arch/linux.c
--- parted-1.9.0/libparted/arch/linux.c.orig	2009-12-14 22:44:18.000000000 +0100
+++ parted-1.9.0/libparted/arch/linux.c	2009-12-15 10:25:38.000000000 +0100
@@ -259,6 +259,7 @@ struct blkdev_ioctl_param {
 #define SX8_MAJOR2              161
 #define XVD_MAJOR               202
 #define SDMMC_MAJOR             179
+#define LOOP_MAJOR              7
 
 #define SCSI_BLK_MAJOR(M) (                                             \
                 (M) == SCSI_DISK0_MAJOR                                 \
@@ -561,6 +562,8 @@ _device_probe_type (PedDevice* dev)
                 dev->type = PED_DEVICE_SDMMC;
         } else if (_is_virtblk_major(dev_major)) {
                 dev->type = PED_DEVICE_VIRTBLK;
+        } else if (dev_major == LOOP_MAJOR) {
+                dev->type = PED_DEVICE_FILE;
         } else {
                 dev->type = PED_DEVICE_UNKNOWN;
         }
@@ -1048,6 +1048,15 @@ init_file (PedDevice* dev)
         if (!ped_device_open (dev))
                 goto error;
 
+        dev->sector_size = PED_SECTOR_SIZE_DEFAULT;
+        char *p = getenv ("PARTED_SECTOR_SIZE");
+        if (p) {
+                int s = atoi (p);
+                if (0 < s && s % 512 == 0)
+                        dev->sector_size = s;
+        }
+        dev->phys_sector_size = dev->sector_size;
+
         if (S_ISBLK(dev_stat.st_mode))
                 dev->length = _device_get_length (dev);
         else