diff --git a/block/parallels.c b/block/parallels.c
index ec89ed894b..3b992e8173 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -136,6 +136,12 @@ static int cluster_remainder(BDRVParallelsState *s, int64_t sector_num,
     return MIN(nb_sectors, ret);
 }
 
+static uint32_t host_cluster_index(BDRVParallelsState *s, int64_t off)
+{
+    off -= s->header->data_off << BDRV_SECTOR_BITS;
+    return off / s->cluster_size;
+}
+
 static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,
                             int nb_sectors, int *pnum)
 {
@@ -533,7 +539,6 @@ parallels_check_leak(BlockDriverState *bs, BdrvCheckResult *res,
 {
     BDRVParallelsState *s = bs->opaque;
     int64_t count, leak_size;
-    int ret;
 
     leak_size = parallels_get_leak_size(bs, res);
     if (leak_size < 0) {
@@ -550,16 +555,123 @@ parallels_check_leak(BlockDriverState *bs, BdrvCheckResult *res,
             fix & BDRV_FIX_LEAKS ? "Repairing" : "ERROR", leak_size);
 
     if (fix & BDRV_FIX_LEAKS) {
-        ret = parallels_fix_leak(bs, res);
-        if (ret < 0) {
-            return ret;
-        }
         res->leaks_fixed += count;
     }
 
     return 0;
 }
 
+static int parallels_check_duplicate(BlockDriverState *bs,
+                                     BdrvCheckResult *res,
+                                     BdrvCheckMode *fix)
+{
+    BDRVParallelsState *s = bs->opaque;
+    QEMUIOVector qiov;
+    int64_t off, sector;
+    unsigned long *bitmap;
+    uint32_t i, bitmap_size, cluster_index;
+    int n, ret = 0;
+    uint64_t *buf = NULL;
+
+    /*
+     * Create a bitmap of used clusters.
+     * If a bit is set, there is a BAT entry pointing to this cluster.
+     * Loop through the BAT entries, check bits relevant to an entry offset.
+     * If bit is set, this entry is duplicated. Otherwise set the bit.
+     *
+     * We shouldn't worry about newly allocated clusters outside the image
+     * because they are created higher then any existing cluster pointed by
+     * a BAT entry.
+     */
+    bitmap_size = host_cluster_index(s, res->image_end_offset);
+    bitmap = bitmap_new(bitmap_size);
+
+    buf = qemu_memalign(4096, s->cluster_size);
+    qemu_iovec_init(&qiov, 0);
+    qemu_iovec_add(&qiov, buf, s->cluster_size);
+
+    for (i = 0; i < s->bat_size; i++) {
+        off = bat2sect(s, i) << BDRV_SECTOR_BITS;
+        if (off == 0) {
+            continue;
+        }
+
+        cluster_index = host_cluster_index(s, off);
+        if (test_bit(cluster_index, bitmap)) {
+            /* this cluster duplicates another one */
+            fprintf(stderr,
+                    "%s duplicate offset in BAT entry %u\n",
+                    *fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR", i);
+
+            res->corruptions++;
+
+            if (*fix & BDRV_FIX_ERRORS) {
+                /*
+                 * Reset the entry and allocate a new cluster
+                 * for the relevant guest offset. In this way we let
+                 * the lower layer to place the new cluster properly.
+                 * Copy the original cluster to the allocated one.
+                 */
+                parallels_set_bat_entry(s, i, 0);
+
+                ret = bdrv_co_pread(bs->file, off, s->cluster_size, buf, 0);
+                if (ret < 0) {
+                    res->check_errors++;
+                    goto out;
+                }
+
+                sector = (i * s->cluster_size) >> BDRV_SECTOR_BITS;
+                sector = allocate_clusters(bs, sector, s->tracks, &n);
+                if (sector < 0) {
+                    res->check_errors++;
+                    ret = sector;
+                    goto out;
+                }
+                off = sector << BDRV_SECTOR_BITS;
+
+                ret = bdrv_co_pwritev(bs->file, off, s->cluster_size, &qiov, 0);
+                if (ret < 0) {
+                    res->check_errors++;
+                    goto out;
+                }
+
+                if (off + s->cluster_size > res->image_end_offset) {
+                    res->image_end_offset = off + s->cluster_size;
+                }
+
+                /*
+                 * In the future allocate_cluster() will reuse holed offsets
+                 * inside the image. Keep the used clusters bitmap content
+                 * consistent for the new allocated clusters too.
+                 *
+                 * Note, clusters allocated outside the current image are not
+                 * considered, and the bitmap size doesn't change.
+                 */
+                cluster_index = host_cluster_index(s, off);
+                if (cluster_index < bitmap_size) {
+                    bitmap_set(bitmap, cluster_index, 1);
+                }
+
+                /*
+                 * When new clusters are allocated, file size increases by
+                 * 128 Mb blocks. We need to truncate the file to the right
+                 * size. Let the leak fix code make its job.
+                 */
+                *fix |= BDRV_FIX_LEAKS;
+                res->corruptions_fixed++;
+            }
+        } else {
+            bitmap_set(bitmap, cluster_index, 1);
+        }
+    }
+
+out:
+    qemu_iovec_destroy(&qiov);
+    g_free(buf);
+    g_free(bitmap);
+    return ret;
+}
+
 static void parallels_collect_statistics(BlockDriverState *bs,
                                          BdrvCheckResult *res,
                                          BdrvCheckMode fix)
@@ -611,7 +723,19 @@ parallels_co_check(BlockDriverState *bs, BdrvCheckResult *res,
             return ret;
         }
 
+        ret = parallels_check_duplicate(bs, res, &fix);
+        if (ret < 0) {
+            return ret;
+        }
+
         parallels_collect_statistics(bs, res, fix);
+
+        if (fix & BDRV_FIX_LEAKS) {
+            ret = parallels_fix_leak(bs, res);
+            if (ret < 0) {
+                return ret;
+            }
+        }
     }
 
     ret = bdrv_co_flush(bs);
