diff --git a/cpu/stm32/cpu_common.c b/cpu/stm32/cpu_common.c
index f1d0055b63..6dbfae8e2a 100644
--- a/cpu/stm32/cpu_common.c
+++ b/cpu/stm32/cpu_common.c
@@ -58,7 +58,7 @@ static const uint8_t apbmul[] = {
 #endif
 };
 
-uint32_t periph_apb_clk(uint8_t bus)
+uint32_t periph_apb_clk(bus_t bus)
 {
 #ifdef CLOCK_APB2
     if (bus == APB2) {
@@ -70,7 +70,7 @@ uint32_t periph_apb_clk(uint8_t bus)
     return CLOCK_APB1;
 }
 
-uint32_t periph_timer_clk(uint8_t bus)
+uint32_t periph_timer_clk(bus_t bus)
 {
     return periph_apb_clk(bus) * apbmul[bus];
 }
diff --git a/cpu/stm32/include/periph/cpu_common.h b/cpu/stm32/include/periph/cpu_common.h
index 527f6c9f5c..16b173c349 100644
--- a/cpu/stm32/include/periph/cpu_common.h
+++ b/cpu/stm32/include/periph/cpu_common.h
@@ -119,7 +119,7 @@ typedef enum {
  *
  * @return              bus clock frequency in Hz
  */
-uint32_t periph_apb_clk(uint8_t bus);
+uint32_t periph_apb_clk(bus_t bus);
 
 /**
  * @brief   Get the actual timer clock frequency
@@ -128,7 +128,7 @@ uint32_t periph_apb_clk(uint8_t bus);
  *
  * @return              timer clock frequency in Hz
  */
-uint32_t periph_timer_clk(uint8_t bus);
+uint32_t periph_timer_clk(bus_t bus);
 
 /**
  * @brief   Enable the given peripheral clock