diff --git a/drivers/isdn/capi/capiutil.c b/drivers/isdn/capi/capiutil.c
index 36c1b37cea0a..9846d82eb097 100644
--- a/drivers/isdn/capi/capiutil.c
+++ b/drivers/isdn/capi/capiutil.c
@@ -201,7 +201,7 @@ static unsigned char *cpars[] =
 #define structTRcpyovl(x, y, l) memmove(y, x, l)
 
 /*-------------------------------------------------------*/
-static unsigned command_2_index(unsigned c, unsigned sc)
+static unsigned command_2_index(u8 c, u8 sc)
 {
 	if (c & 0x80)
 		c = 0x9 + (c & 0x0f);