diff --git a/uart.hpp b/uart.hpp
index e5adff3..6f51869 100644
--- a/uart.hpp
+++ b/uart.hpp
@@ -134,7 +134,7 @@ class Uart {
 		data_t *bufEnd = buffer + numDigits - 1;
 
 		do {
-			data_t lastDigit = digits % Base;
+			const data_t lastDigit = digits % Base;
 			*bufEnd-- = (lastDigit < 10) ? ('0' + lastDigit) : (alphaChar + lastDigit - 10);
 			digits /= Base;
 		} while (digits > 0);