diff --git a/block/io.c b/block/io.c
index fbcd93304be1cdc50c538c2ec3e211e470e65163..6293612e73c10a6bc9e318235477fb03b15014e9 100644
--- a/block/io.c
+++ b/block/io.c
@@ -601,9 +601,11 @@ static void tracked_request_end(BdrvTrackedRequest *req)
 static void tracked_request_begin(BdrvTrackedRequest *req,
                                   BlockDriverState *bs,
                                   int64_t offset,
-                                  unsigned int bytes,
+                                  uint64_t bytes,
                                   enum BdrvTrackedRequestType type)
 {
+    assert(bytes <= INT64_MAX && offset <= INT64_MAX - bytes);
+
     *req = (BdrvTrackedRequest){
         .bs = bs,
         .offset         = offset,
@@ -625,7 +627,7 @@ static void tracked_request_begin(BdrvTrackedRequest *req,
 static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
 {
     int64_t overlap_offset = req->offset & ~(align - 1);
-    unsigned int overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
+    uint64_t overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
                                - overlap_offset;
 
     if (!req->serialising) {
@@ -683,7 +685,7 @@ static int bdrv_get_cluster_size(BlockDriverState *bs)
 }
 
 static bool tracked_request_overlaps(BdrvTrackedRequest *req,
-                                     int64_t offset, unsigned int bytes)
+                                     int64_t offset, uint64_t bytes)
 {
     /*        aaaa   bbbb */
     if (offset >= req->overlap_offset + req->overlap_bytes) {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 920d3d122b50354d9780aabb13b58f9a336a4671..903b9c1034a1ef668af1a3f9b449e98622df3c6d 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -69,12 +69,12 @@ enum BdrvTrackedRequestType {
 typedef struct BdrvTrackedRequest {
     BlockDriverState *bs;
     int64_t offset;
-    unsigned int bytes;
+    uint64_t bytes;
     enum BdrvTrackedRequestType type;
 
     bool serialising;
     int64_t overlap_offset;
-    unsigned int overlap_bytes;
+    uint64_t overlap_bytes;
 
     QLIST_ENTRY(BdrvTrackedRequest) list;
     Coroutine *co; /* owner, used for deadlock detection */