diff --git a/arch/arm/src/stm32/stm32_rcc.c b/arch/arm/src/stm32/stm32_rcc.c
index 3bd2913076f..553f76e73df 100644
--- a/arch/arm/src/stm32/stm32_rcc.c
+++ b/arch/arm/src/stm32/stm32_rcc.c
@@ -119,7 +119,7 @@
  ****************************************************************************/
 
 #if defined(CONFIG_RTC) && defined(CONFIG_STM32_PWR) && !defined(CONFIG_STM32_STM32F10XX)
-static inline rcc_resetbkp(void)
+static inline void rcc_resetbkp(void)
 {
   uint32_t regval;
 
diff --git a/arch/arm/src/stm32l4/stm32l4_rcc.c b/arch/arm/src/stm32l4/stm32l4_rcc.c
index b972c2680b4..34e6052eefe 100644
--- a/arch/arm/src/stm32l4/stm32l4_rcc.c
+++ b/arch/arm/src/stm32l4/stm32l4_rcc.c
@@ -106,7 +106,7 @@
  ****************************************************************************/
 
 #if defined(CONFIG_STM32_PWR) && defined(CONFIG_RTC)
-static inline rcc_resetbkp(void)
+static inline void rcc_resetbkp(void)
 {
   bool init_stat;