diff --git a/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp b/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
index 74969a0750..b2885bfe26 100644
--- a/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
+++ b/libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp
@@ -25,6 +25,7 @@
 #include "shared_dma.h"
 #include "sdcard.h"
 #include "hwdef/common/usbcfg.h"
+#include "hwdef/common/stm32_util.h"
 
 #include <hwdef.h>
 
@@ -176,6 +177,8 @@ 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 1ba5c1ef07..57e2645281 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c
@@ -251,3 +251,17 @@ void set_fast_reboot(enum rtc_boot_magic v)
 {
     set_rtc_backup0(v);
 }
+
+/*
+  enable peripheral power if needed This is done late to prevent
+  problems with RTS causing SiK radios to stay in the bootloader
+*/
+void peripheral_power_enable(void)
+{
+#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
+}
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h
index 2caa4c4d4d..d9c4c4be29 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h
@@ -64,6 +64,9 @@ enum rtc_boot_magic check_fast_reboot(void);
 
 // set RTC register for a fast reboot
 void set_fast_reboot(enum rtc_boot_magic v);
+
+// enable peripheral power if needed
+void peripheral_power_enable(void);
     
 #ifdef __cplusplus
 }
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/fmuv5/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/fmuv5/hwdef.dat
index a28c246624..d3433e708e 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/fmuv5/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/fmuv5/hwdef.dat
@@ -94,8 +94,13 @@ I2C_ORDER I2C3 I2C1 I2C2 I2C4
 
 # enable pins
 PE3 VDD_3V3_SENSORS_EN OUTPUT HIGH
-PF12 nVDD_5V_HIPOWER_EN OUTPUT LOW
-PG4  nVDD_5V_PERIPH_EN OUTPUT LOW
+
+# start peripheral power off, then enable after init
+# this prevents a problem with radios that use RTS for
+# bootloader hold
+PF12 nVDD_5V_HIPOWER_EN OUTPUT HIGH
+PG4  nVDD_5V_PERIPH_EN OUTPUT HIGH
+
 PG5  VDD_5V_RC_EN OUTPUT HIGH
 PG6  VDD_5V_WIFI_EN OUTPUT HIGH
 PG7  VDD_3V3_SD_CARD_EN OUTPUT HIGH