diff --git a/compilers/concrete-compiler/compiler/lib/Runtime/GPUDFG.cpp b/compilers/concrete-compiler/compiler/lib/Runtime/GPUDFG.cpp
index 06e7b33188..4fb6e849fd 100644
--- a/compilers/concrete-compiler/compiler/lib/Runtime/GPUDFG.cpp
+++ b/compilers/concrete-compiler/compiler/lib/Runtime/GPUDFG.cpp
@@ -1085,7 +1085,7 @@ void memref_keyswitch_lwe_u64_process(Process *p, int32_t loc, int32_t chunk_id,
       for (uint32_t i = 0; i < num_samples; i++) {
 	indexes[i] = i;
       }
-      void *indexes_gpu = alloc_and_memcpy_async_to_gpu(indexes, 0, num_samples * sizeof(uint64_t), loc, s);
+      void *indexes_gpu = alloc_and_memcpy_async_to_gpu(indexes, 0, num_samples, loc, s);
 
       cuda_keyswitch_lwe_ciphertext_vector_64(
 	  s, loc, out_gpu, indexes_gpu, ct0_gpu, indexes_gpu, ksk_gpu, p->input_lwe_dim.val,
@@ -1192,7 +1192,7 @@ void memref_bootstrap_lwe_u64_process(Process *p, int32_t loc, int32_t chunk_id,
       for (uint32_t i = 0; i < num_samples; i++) {
 	indexes[i] = i;
       }
-      void *indexes_gpu = alloc_and_memcpy_async_to_gpu(indexes, 0, num_samples * sizeof(uint64_t), loc, s);
+      void *indexes_gpu = alloc_and_memcpy_async_to_gpu(indexes, 0, num_samples, loc, s);
 
       int8_t *pbs_buffer = p->dfg->gpus[loc].get_pbs_buffer(
           p->glwe_dim.val, p->poly_size.val, num_samples);