diff --git a/GrandBrownTown.cu b/GrandBrownTown.cu
index 06b99a500787f69a015863292712c2d6d8e3bd43..995df0bbe6f670876767ece82a360b221e571eaa 100644
--- a/GrandBrownTown.cu
+++ b/GrandBrownTown.cu
@@ -945,7 +945,7 @@ void GrandBrownTown::copyToCUDA() {
 														cudaMemcpyHostToDevice));
 
 	gpuErrchk(cudaMalloc(&forceInternal_d, sizeof(Vector3) * num * numReplicas));
-	gpuErrchk(cudaMemcpyAsync(forceInternal_d, forceInternal, sizeof(Vector3),
+	gpuErrchk(cudaMemcpyAsync(forceInternal_d, forceInternal, sizeof(Vector3) * tot_num,
 														cudaMemcpyHostToDevice));
 
 	gpuErrchk(cudaMalloc(&randoGen_d, sizeof(Random)));