Cleanup for GCC-4.x
diff --git a/board/amcc/walnut/walnut.c b/board/amcc/walnut/walnut.c
index 9fca0a6..f1a96a6 100644
--- a/board/amcc/walnut/walnut.c
+++ b/board/amcc/walnut/walnut.c
@@ -67,7 +67,7 @@
  */
 int checkboard(void)
 {
-	unsigned char *s = getenv("serial#");
+	char *s = getenv("serial#");
 	uint pvr = get_pvr();
 
 	if (pvr == PVR_405GPR_RB) {