diff --git a/thrust/system/cuda/detail/scan_by_key.h b/thrust/system/cuda/detail/scan_by_key.h
index fe4b321c0..edf579695 100644
--- a/thrust/system/cuda/detail/scan_by_key.h
+++ b/thrust/system/cuda/detail/scan_by_key.h
@@ -513,7 +513,7 @@ namespace __scan_by_key {
             scan_op(scan_op_)
       {
         int  tile_idx      = blockIdx.x;
-        Size tile_base     = ITEMS_PER_TILE * tile_idx;
+        Size tile_base     = ITEMS_PER_TILE * static_cast<Size>(tile_idx);
         Size num_remaining = num_items - tile_base;
 
         if (num_remaining > ITEMS_PER_TILE)
@@ -734,7 +734,7 @@ namespace __scan_by_key {
                              ScanOp                     scan_op,
                              AddInitToScan              add_init_to_scan)
   {
-    int          num_items    = static_cast<int>(thrust::distance(keys_first, keys_last));
+    size_t       num_items    = static_cast<size_t>(thrust::distance(keys_first, keys_last));
     size_t       storage_size = 0;
     cudaStream_t stream       = cuda_cub::stream(policy);
     bool         debug_sync   = THRUST_DEBUG_SYNC_FLAG;