diff --git a/software/common/validation/uart_tests.c b/software/common/validation/uart_tests.c
index 551276ddc79ba6ad6e2450aaff4c02485227a4be..9811537ea4ce52ffa8f002071531ce0317db68f1 100644
--- a/software/common/validation/uart_tests.c
+++ b/software/common/validation/uart_tests.c
@@ -952,7 +952,7 @@ int uart2_interrupt_test(void){
   int return_val=0;
   int err_code=0;
   int i;
-  char ctmp; /* dummy variable for overflow test (data can be corrupted so it is not checked) */
+  char volatile ctmp; /* dummy variable for overflow test (data can be corrupted so it is not checked) */
 
 
   puts ("UART 2 interrupt connectivity test");