diff --git a/target/linux/lantiq/image/lzma-loader/src/printf.c b/target/linux/lantiq/image/lzma-loader/src/printf.c
index 7bb5a86e187..31b5e19ab14 100644
--- a/target/linux/lantiq/image/lzma-loader/src/printf.c
+++ b/target/linux/lantiq/image/lzma-loader/src/printf.c
@@ -11,7 +11,7 @@
 
 #include	"printf.h"
 
-extern void board_putc(int ch);
+extern void board_putc(char ch);
 
 /* this is the maximum width for a variable */
 #define		LP_MAX_BUF	256