diff --git a/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp b/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
index b2885bfe26..1a06afda42 100644
--- a/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
+++ b/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
@@ -153,7 +153,9 @@ static THD_FUNCTION(main_loop,arg)
 #endif
 
     ChibiOS::Shared_DMA::init();
-    
+
+    peripheral_power_enable();
+        
     hal.uartA->begin(115200);
 
 #ifdef HAL_SPI_CHECK_CLOCK_FREQ
@@ -177,8 +179,6 @@ static THD_FUNCTION(main_loop,arg)
 
     schedulerInstance.hal_initialized();
 
-    peripheral_power_enable();
-    
     g_callbacks->setup();
     hal.scheduler->system_initialized();
 
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c
index 57e2645281..23f4b9353d 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c
@@ -254,14 +254,24 @@ void set_fast_reboot(enum rtc_boot_magic v)
 
 /*
   enable peripheral power if needed This is done late to prevent
-  problems with RTS causing SiK radios to stay in the bootloader
+  problems with CTS causing SiK radios to stay in the bootloader. A
+  SiK radio will stay in the bootloader if CTS is held to GND on boot
 */
 void peripheral_power_enable(void)
 {
+#if defined(HAL_GPIO_PIN_nVDD_5V_PERIPH_EN) || defined(HAL_GPIO_PIN_nVDD_5V_HIPOWER_EN)
+    // we don't know what state the bootloader had the CTS pin in, so
+    // wait here with it pulled up from the PAL table for enough time
+    // for the radio to be definately powered down
+    for (uint8_t i=0; i<100; i++) {
+        // use a loop as this may be a 16 bit timer
+        chThdSleep(MS2ST(1));
+    }
 #ifdef HAL_GPIO_PIN_nVDD_5V_PERIPH_EN
     palWriteLine(HAL_GPIO_PIN_nVDD_5V_PERIPH_EN, 0);
 #endif
 #ifdef HAL_GPIO_PIN_nVDD_5V_HIPOWER_EN
     palWriteLine(HAL_GPIO_PIN_nVDD_5V_HIPOWER_EN, 0);
 #endif
+#endif
 }