diff --git a/src/pk/asn1/der/utf8/der_decode_utf8_string.c b/src/pk/asn1/der/utf8/der_decode_utf8_string.c
index 94555b99..d3ed82be 100644
--- a/src/pk/asn1/der/utf8/der_decode_utf8_string.c
+++ b/src/pk/asn1/der/utf8/der_decode_utf8_string.c
@@ -65,7 +65,7 @@ int der_decode_utf8_string(const unsigned char *in,  unsigned long inlen,
       /* count number of bytes */
       for (z = 0; (tmp & 0x80) && (z <= 4); z++, tmp = (tmp << 1) & 0xFF);
 
-      if (z > 4 || (x + (z - 1) > inlen)) {
+      if (z == 1 || z > 4 || (x + (z - 1) > inlen)) {
          return CRYPT_INVALID_PACKET;
       }