diff --git a/src/shellmatta.c b/src/shellmatta.c
index 59ac79e..35b1fce 100644
--- a/src/shellmatta.c
+++ b/src/shellmatta.c
@@ -97,7 +97,7 @@ static uint32_t shellItoa(int32_t value, char *buffer, uint32_t base)
         do
         {
             digitValue = (char) (value % base);
-            tempBuffer[i] = (digitValue < 10u) ? ('0' + digitValue) : ('A' + digitValue);
+            tempBuffer[i] = (digitValue < 10u) ? ('0' + digitValue) : (('A' - 10) + digitValue);
             value /= base;
             i ++;
         }while(value > 0);