diff --git a/demos/ARMCM3-STM32F103-GCC/board.c b/demos/ARMCM3-STM32F103-GCC/board.c
index d3e776d1a..7ce9248cd 100644
--- a/demos/ARMCM3-STM32F103-GCC/board.c
+++ b/demos/ARMCM3-STM32F103-GCC/board.c
@@ -61,7 +61,7 @@ void hwinit0(void) {
   /*
    * I/O ports initialization as specified in board.h.
    */
-  RCC->APB2ENR = 0x0000003D;    // Ports A-D enabled, AFIO enabled.
+  ioport_init();
   GPIOA->CRL = VAL_GPIOACRL;
   GPIOA->CRH = VAL_GPIOACRH;
   GPIOA->ODR = VAL_GPIOAODR;
diff --git a/ports/ARMCM3-STM32F103/ioports_lld.h b/ports/ARMCM3-STM32F103/ioports_lld.h
index 2194c3869..fd028e4d3 100644
--- a/ports/ARMCM3-STM32F103/ioports_lld.h
+++ b/ports/ARMCM3-STM32F103/ioports_lld.h
@@ -107,6 +107,16 @@ typedef GPIO_TypeDef * ioportid_t;
 /* functions, please put them in a file named ioports_lld.c if so.           */
 /*===========================================================================*/
 
+/**
+ * @brief GPIO ports subsystem initialization.
+ * @details Ports A-D enabled, AFIO enabled.
+ */
+#define ioport_init() {                                                 \
+  RCC->APB2ENR |= RCC_APB2ENR_AFIOEN | RCC_APB2ENR_IOPAEN |             \
+                  RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN |             \
+                  RCC_APB2ENR_IOPDEN;                                   \
+}
+
 /**
  * @brief Writes a bits mask on a I/O port.
  *
diff --git a/src/templates/ioports_lld.h b/src/templates/ioports_lld.h
index 708efc8b7..a046446f5 100644
--- a/src/templates/ioports_lld.h
+++ b/src/templates/ioports_lld.h
@@ -65,6 +65,14 @@ typedef uint32_t ioportid_t;
 /* functions, please put them in a file named ioports_lld.c if so.           */
 /*===========================================================================*/
 
+/**
+ * @brief I/O ports subsystem initialization.
+ *
+ * @note This function is not invoked by a system API, it should be invoked
+ *       from the system initialization code.
+ */
+#define ioport_init()
+
 /**
  * @brief Writes a bits mask on a I/O port.
  *