diff --git a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
index e9641ea7e4771c1bdef753d115ec42c9a844f32c..fcfcda7ff1f4a39621b1d407fe32dbcb10912bf4 100644
--- a/drivers/staging/panel/panel.c
+++ b/drivers/staging/panel/panel.c
@@ -2065,7 +2065,7 @@ static u8 input_name2mask(const char *name, __u64 *mask, __u64 *value,
 		im |= BIT(in);
 
 		name++;
-		if (isdigit(*name)) {
+		if (*name >= '0' && *name <= '7') {
 			out = *name - '0';
 			om |= BIT(out);
 		} else if (*name == '-') {