diff --git a/lib_xud/src/core/XUD_Main.xc b/lib_xud/src/core/XUD_Main.xc
index 5709c77d..55fbfdc3 100755
--- a/lib_xud/src/core/XUD_Main.xc
+++ b/lib_xud/src/core/XUD_Main.xc
@@ -394,16 +394,12 @@ static int XUD_Manager_loop(XUD_chan epChans0[], XUD_chan epAddr_Ready[],  chane
 
             XUD_HAL_Mode_DataTransfer();
 
-            set_thread_fast_mode_on();
-
             /* Run main IO loop */
             /* flag0: Rx Error
                flag1: Rx Active
                flag2: Null / Valid Token  */
             noExit = XUD_LLD_IoLoop(p_usb_rxd, flag1_port, p_usb_txd, flag0_port, flag2_port, epTypeTableOut, epTypeTableIn, epAddr_Ready, noEpOut, c_sof);
 
-            set_thread_fast_mode_off();
-
             if(!noExit)
                 break;
         }
@@ -567,6 +563,8 @@ int XUD_Main(chanend c_ep_out[], int noEpOut,
                 XUD_EpType epTypeTableOut[], XUD_EpType epTypeTableIn[],
                 XUD_BusSpeed_t speed, XUD_PwrConfig pwrConfig)
 {
+    set_core_high_priority_on();
+
     g_desSpeed = speed;
 
     SetupEndpoints(c_ep_out, noEpOut, c_ep_in, noEpIn, epTypeTableOut, epTypeTableIn);