diff --git a/board/esd/wuh405/wuh405.c b/board/esd/wuh405/wuh405.c
index 09c4d36..db24122 100644
--- a/board/esd/wuh405/wuh405.c
+++ b/board/esd/wuh405/wuh405.c
@@ -193,7 +193,7 @@
 
 int checkboard (void)
 {
-	unsigned char str[64];
+	char str[64];
 	int i = getenv_r ("serial#", str, sizeof(str));
 
 	puts ("Board: ");