diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 1f5ea82b58bf..213655aa6e48 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -385,7 +385,8 @@ static bool is_an_alpha2(const char *alpha2)
 {
 	if (!alpha2)
 		return false;
-	return isalpha(alpha2[0]) && isalpha(alpha2[1]);
+	return isascii(alpha2[0]) && isalpha(alpha2[0]) &&
+	       isascii(alpha2[1]) && isalpha(alpha2[1]);
 }
 
 static bool alpha2_equal(const char *alpha2_x, const char *alpha2_y)