diff --git a/crypto/x509/a_strex.c b/crypto/x509/a_strex.c
index aa2501a4..d0d83564 100644
--- a/crypto/x509/a_strex.c
+++ b/crypto/x509/a_strex.c
@@ -321,7 +321,7 @@ static const signed char tag2nbyte[] = {
     -1, -1, -1, -1, -1,         /* 5-9 */
     -1, -1, 0, -1,              /* 10-13 */
     -1, -1, -1, -1,             /* 15-17 */
-    -1, 1, 1,                   /* 18-20 */
+    1, 1, 1,                    /* 18-20 */
     -1, 1, 1, 1,                /* 21-24 */
     -1, 1, -1,                  /* 25-27 */
     4, -1, 2                    /* 28-30 */