diff --git a/bsp/src/bsp_ml307.c b/bsp/src/bsp_ml307.c
index 76d9e0f..31cd14a 100644
--- a/bsp/src/bsp_ml307.c
+++ b/bsp/src/bsp_ml307.c
@@ -318,7 +318,8 @@ uint8_t bcd_to_dec(uint8_t bcd)
 
 int test(int argc, char **argv)
 {
-    uint8_t b   = atoi(argv[1]);
+    uint8_t a = atoi(argv[1]);
+    rt_uint8_t b = a;
 
     LOG_D("in = 0x%02X, %d", a, a);
     b = a;