diff --git a/src/spike_mpi.cu b/src/spike_mpi.cu
index addd658de..05a829e92 100644
--- a/src/spike_mpi.cu
+++ b/src/spike_mpi.cu
@@ -329,6 +329,8 @@ ConnectMpi::SendSpikeToRemote( int n_hosts, int max_spike_per_host )
 
     // nonblocking sent of spike packet to MPI proc ih
     MPI_Isend( &h_ExternalTargetSpikeNodeId[ array_idx ], n_spikes, MPI_INT, ih, tag, MPI_COMM_WORLD, &request );
+    MPI_Request_free(&request);
+
     // printf("MPI_Send nspikes (src,tgt,nspike): "
     //	   "%d %d %d\n", mpi_id, ih, n_spikes);
     // printf("MPI_Send 1st-neuron-idx (src,tgt,idx): "