diff --git a/src/platforms/stm32/serialno.c b/src/platforms/stm32/serialno.c
index 574fce0..67776cf 100644
--- a/src/platforms/stm32/serialno.c
+++ b/src/platforms/stm32/serialno.c
@@ -23,7 +23,7 @@
 char *serial_no_read(char *s)
 {
 #if DFU_SERIAL_LENGTH == 9
-	const volatile uint32_t *const unique_id_p = (volatile uint32_t *)DESIG_UNIQUE_ID_BASE;
+	const volatile uint32_t *const unique_id_p = (uint32_t *)DESIG_UNIQUE_ID_BASE;
 	const uint32_t unique_id = unique_id_p[0] + unique_id_p[1] + unique_id_p[2];
 	/* Fetch serial number from chip's unique ID */
 	for(size_t i = 0; i < 8U; ++i) {
@@ -34,7 +34,7 @@ char *serial_no_read(char *s)
 	}
 #elif DFU_SERIAL_LENGTH == 13
 	/* Use the same serial number as the ST DFU Bootloader.*/
-	const uint16_t *const uid = (uint16_t *)DESIG_UNIQUE_ID_BASE;
+	const volatile uint16_t *const uid = (uint16_t *)DESIG_UNIQUE_ID_BASE;
 # if defined(STM32F4) || defined(STM32F7)
 	int offset = 3;
 # elif defined(STM32L0) ||  defined(STM32F0) || defined(STM32F3)
@@ -42,7 +42,7 @@ char *serial_no_read(char *s)
 # endif
 	sprintf(s, "%04X%04X%04X", uid[1] + uid[5], uid[0] + uid[4], uid[offset]);
 #elif DFU_SERIAL_LENGTH == 25
-	volatile uint32_t *unique_id_p = (uint32_t *)DESIG_UNIQUE_ID_BASE;
+	const volatile uint32_t *const unique_id_p = (uint32_t *)DESIG_UNIQUE_ID_BASE;
 	uint32_t unique_id = 0;
 	for (size_t i = 0; i < 24U; ++i) {
 		const size_t chunk = i >> 3U;