diff --git a/toxcore/net_crypto.c b/toxcore/net_crypto.c
index 87541d9fd..7ad3b4131 100644
--- a/toxcore/net_crypto.c
+++ b/toxcore/net_crypto.c
@@ -830,7 +830,9 @@ static int64_t send_lossless_packet(Net_Crypto *c, int crypt_connection_id, cons
     dt.time = 0;
     dt.length = length;
     memcpy(dt.data, data, length);
+    pthread_mutex_lock(&conn->mutex);
     int64_t packet_num = add_data_end_of_buffer(&conn->send_array, &dt);
+    pthread_mutex_unlock(&conn->mutex);
 
     if (packet_num == -1)
         return -1;
@@ -2593,8 +2595,11 @@ int send_lossy_cryptpacket(Net_Crypto *c, int crypt_connection_id, const uint8_t
     int ret = -1;
 
     if (conn) {
-        ret = send_data_packet_helper(c, crypt_connection_id, conn->recv_array.buffer_start, conn->send_array.buffer_end, data,
-                                      length);
+        pthread_mutex_lock(&conn->mutex);
+        uint32_t buffer_start = conn->recv_array.buffer_start;
+        uint32_t buffer_end = conn->send_array.buffer_end;
+        pthread_mutex_unlock(&conn->mutex);
+        ret = send_data_packet_helper(c, crypt_connection_id, buffer_start, buffer_end, data, length);
     }
 
     pthread_mutex_lock(&c->connections_mutex);