diff --git a/port/dwc2/usb_dc_dwc2.c b/port/dwc2/usb_dc_dwc2.c
index e7d3feab..f05207c4 100644
--- a/port/dwc2/usb_dc_dwc2.c
+++ b/port/dwc2/usb_dc_dwc2.c
@@ -191,7 +191,7 @@ USB_NOCACHE_RAM_SECTION struct dwc2_udc {
 
 static inline int dwc2_reset(void)
 {
-    uint32_t count = 0U;
+    volatile uint32_t count = 0U;
 
     /* Wait for AHB master IDLE state. */
     do {
@@ -252,7 +252,7 @@ static inline void dwc2_set_mode(uint8_t mode)
 
 static inline int dwc2_flush_rxfifo(void)
 {
-    uint32_t count = 0;
+    volatile uint32_t count = 0;
 
     USB_OTG_GLB->GRSTCTL = USB_OTG_GRSTCTL_RXFFLSH;
 
@@ -267,7 +267,7 @@ static inline int dwc2_flush_rxfifo(void)
 
 static inline int dwc2_flush_txfifo(uint32_t num)
 {
-    uint32_t count = 0U;
+    volatile uint32_t count = 0U;
 
     USB_OTG_GLB->GRSTCTL = (USB_OTG_GRSTCTL_TXFFLSH | (num << 6));
 
diff --git a/port/dwc2/usb_hc_dwc2.c b/port/dwc2/usb_hc_dwc2.c
index 1f18771f..7c51eaa7 100644
--- a/port/dwc2/usb_hc_dwc2.c
+++ b/port/dwc2/usb_hc_dwc2.c
@@ -66,7 +66,7 @@ struct dwc2_hcd {
 
 static inline int dwc2_reset(void)
 {
-    uint32_t count = 0U;
+    volatile uint32_t count = 0U;
 
     /* Wait for AHB master IDLE state. */
     do {
@@ -127,7 +127,7 @@ static inline void dwc2_set_mode(uint8_t mode)
 
 static inline int dwc2_flush_rxfifo(void)
 {
-    uint32_t count = 0;
+    volatile uint32_t count = 0;
 
     USB_OTG_GLB->GRSTCTL = USB_OTG_GRSTCTL_RXFFLSH;
 
@@ -142,7 +142,7 @@ static inline int dwc2_flush_rxfifo(void)
 
 static inline int dwc2_flush_txfifo(uint32_t num)
 {
-    uint32_t count = 0U;
+    volatile uint32_t count = 0U;
 
     USB_OTG_GLB->GRSTCTL = (USB_OTG_GRSTCTL_TXFFLSH | (num << 6));