diff --git a/src/pk/asn1/der/utf8/der_length_utf8_string.c b/src/pk/asn1/der/utf8/der_length_utf8_string.c
index 1135acc..3a8ef06 100644
--- a/src/pk/asn1/der/utf8/der_length_utf8_string.c
+++ b/src/pk/asn1/der/utf8/der_length_utf8_string.c
@@ -48,10 +48,10 @@ unsigned long der_utf8_charsize(const wchar_t c)
 int der_utf8_valid_char(const wchar_t c)
 {
 #if !defined(__WCHAR_MAX__) || __WCHAR_MAX__ > 0xFFFF
-   if (in[x] > 0x10FFFF) return 0;
+   if (c > 0x10FFFF) return 0;
 #endif
 #if !defined(__WCHAR_MAX__) || __WCHAR_MAX__ != 0xFFFF && __WCHAR_MAX__ != 0xFFFFFFFF
-   if (in[x] < 0) return 0;
+   if (c < 0) return 0;
 #endif
    return 1;
 }