diff --git a/platforms/posix/src/hci_transport_h4.c b/platforms/posix/src/hci_transport_h4.c
index a545ddc0e..e4ce63ba0 100644
--- a/platforms/posix/src/hci_transport_h4.c
+++ b/platforms/posix/src/hci_transport_h4.c
@@ -56,6 +56,11 @@
 #include "hci.h"
 #include "hci_transport.h"
 
+// assert pre-buffer for packet type is available
+#if !defined(HCI_OUTGOING_PRE_BUFFER_SIZE) || (HCI_OUTGOING_PRE_BUFFER_SIZE == 0)
+#error HCI_OUTGOING_PRE_BUFFER_SIZE not defined. Please update hci.h
+#endif
+
 static int  h4_process(struct data_source *ds);
 static void dummy_handler(uint8_t packet_type, uint8_t *packet, uint16_t size); 
 static      hci_uart_config_t *hci_uart_config;
@@ -206,23 +211,13 @@ static int h4_send_packet(uint8_t packet_type, uint8_t * packet, int size){
     if (hci_transport_h4->ds == NULL) return -1;
     if (hci_transport_h4->uart_fd == 0) return -1;
 
+    // store packet type before actual data and increase size
     char *data = (char*) packet;
-    int bytes_written;
-#if HCI_OUTGOING_PRE_BUFFER_SIZE > 0
-    // just store packet type before actual data and increase size
     size++;
     data--;
     *data = packet_type;
-#else
-    // write out single byte
-    bytes_written = write(hci_transport_h4->uart_fd, &packet_type, 1);
-    while (bytes_written < 1) {
-        usleep(5000);
-        bytes_written = write(hci_transport_h4->uart_fd, &packet_type, 1);
-    };
-#endif
     while (size > 0) {
-        bytes_written = write(hci_transport_h4->uart_fd, data, size);
+        int bytes_written = write(hci_transport_h4->uart_fd, data, size);
         if (bytes_written < 0) {
             usleep(5000);
             continue;