diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
index 486591bf071a94045ad1c6d1e75f28879ab0798a..797787823e0672cb57c5ba1b24f017c9394c5fd7 100644
--- a/hw/char/cadence_uart.c
+++ b/hw/char/cadence_uart.c
@@ -375,6 +375,9 @@ static void uart_write(void *opaque, hwaddr offset,
 
     DB_PRINT(" offset:%x data:%08x\n", (unsigned)offset, (unsigned)value);
     offset >>= 2;
+    if (offset >= CADENCE_UART_R_MAX) {
+        return;
+    }
     switch (offset) {
     case R_IER: /* ier (wts imr) */
         s->r[R_IMR] |= value;