diff --git a/block/parallels.c b/block/parallels.c
index dbcaf5d310..339ce45634 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -136,6 +136,26 @@ 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 highest_offset(BDRVParallelsState *s)
+{
+    int64_t off, high_off = 0;
+    int i;
+
+    for (i = 0; i < s->bat_size; i++) {
+        off = bat2sect(s, i) << BDRV_SECTOR_BITS;
+        if (off > high_off) {
+            high_off = off;
+        }
+    }
+    return high_off;
+}
+
 static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,
                             int nb_sectors, int *pnum)
 {
@@ -547,6 +567,114 @@ static int parallels_check_leak(BlockDriverState *bs,
     return 0;
 }
 
+static int parallels_check_duplicate(BlockDriverState *bs,
+                                     BdrvCheckResult *res,
+                                     BdrvCheckMode fix)
+{
+    BDRVParallelsState *s = bs->opaque;
+    QEMUIOVector qiov;
+    int64_t off, high_off, sector;
+    unsigned long *bitmap;
+    uint32_t i, bitmap_size, cluster_index;
+    int n, ret = 0;
+    uint64_t *buf = NULL;
+    bool new_allocations = false;
+
+    high_off = highest_offset(s);
+    if (high_off == 0) {
+        return 0;
+    }
+
+    /*
+     * Create a bitmap of used clusters.
+     * If a bit is set, there is a BAT entry pointing to this cluster.
+     * Loop through the BAT entrues, check bits relevant to an entry offset.
+     * If bit is set, this entry is duplicated. Otherwise set the bit.
+     */
+    bitmap_size = host_cluster_index(s, high_off) + 1;
+    bitmap = bitmap_new(bitmap_size);
+
+    buf = g_malloc(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_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;
+                off = allocate_clusters(bs, sector, s->tracks, &n);
+                if (off < 0) {
+                    res->check_errors++;
+                    ret = off;
+                    goto out;
+                }
+                off <<= BDRV_SECTOR_BITS;
+                if (off > high_off) {
+                    high_off = off;
+                }
+
+                ret = bdrv_co_pwritev(bs->file, off, s->cluster_size, &qiov, 0);
+                if (ret < 0) {
+                    res->check_errors++;
+                    goto out;
+                }
+
+                new_allocations = true;
+                res->corruptions_fixed++;
+            }
+
+        } else {
+            bitmap_set(bitmap, cluster_index, 1);
+        }
+    }
+
+    if (new_allocations) {
+        /*
+         * When new clusters are allocated, file size increases
+         * by 128 Mb blocks. We need to truncate the file to the
+         * right size.
+         */
+        ret = parallels_handle_leak(bs, res, high_off, true);
+        if (ret < 0) {
+            res->check_errors++;
+            goto out;
+        }
+    }
+
+out:
+    qemu_iovec_destroy(&qiov);
+    g_free(buf);
+    g_free(bitmap);
+    return ret;
+}
+
 static void parallels_collect_statistics(BlockDriverState *bs,
                                          BdrvCheckResult *res,
                                          BdrvCheckMode fix)
@@ -595,6 +723,14 @@ static int coroutine_fn parallels_co_check(BlockDriverState *bs,
             return ret;
         }
 
+        /* This checks only for "WithouFreSpacExt" format */
+        if (!memcmp(s->header->magic, HEADER_MAGIC2, 16)) {
+            ret = parallels_check_duplicate(bs, res, fix);
+            if (ret < 0) {
+                return ret;
+            }
+        }
+
         parallels_collect_statistics(bs, res, fix);
     }
 
