diff --git a/apps/apps.c b/apps/apps.c
index 97f0c0e182b36959f1c0df8a56b1d8e8d42fd991..bf044d40f85ae2456f7d4ffe60217424eb637e54 100644
--- a/apps/apps.c
+++ b/apps/apps.c
@@ -2780,7 +2780,7 @@ void print_cert_checks(BIO *bio, X509 *x,
         return;
     if (checkhost) {
         BIO_printf(bio, "Hostname %s does%s match certificate\n",
-                   checkhost, X509_check_host(x, checkhost, 0, 0, NULL)
+                   checkhost, X509_check_host(x, checkhost, 0, 0, NULL) == 1
                    ? "" : " NOT");
     }
 
diff --git a/crypto/x509v3/v3_utl.c b/crypto/x509v3/v3_utl.c
index 1ad3999c92e5fe53674c9fd082843ba3580f8d59..cd7a9809ca31e8eb835c841682b183bb911c84b3 100644
--- a/crypto/x509v3/v3_utl.c
+++ b/crypto/x509v3/v3_utl.c
@@ -889,8 +889,13 @@ static int do_check_string(ASN1_STRING *a, int cmp_type, equal_fn equal,
         int astrlen;
         unsigned char *astr;
         astrlen = ASN1_STRING_to_UTF8(&astr, a);
-        if (astrlen < 0)
+        if (astrlen < 0) {
+            /*
+             * -1 could be an internal malloc failure or a decoding error from
+             * malformed input; we can't distinguish.
+             */
             return -1;
+        }
         rv = equal(astr, astrlen, (unsigned char *)b, blen, flags);
         if (rv > 0 && peername)
             *peername = BUF_strndup((char *)astr, astrlen);
diff --git a/doc/crypto/X509_check_host.pod b/doc/crypto/X509_check_host.pod
index f8b530df9b5615a3e63f7ca1858580089e462d55..0def17aac1c54a49f734c7ccc03f3b8977d568e6 100644
--- a/doc/crypto/X509_check_host.pod
+++ b/doc/crypto/X509_check_host.pod
@@ -109,9 +109,12 @@ but would not match a peer certificate with a DNS name of
 =head1 RETURN VALUES
 
 The functions return 1 for a successful match, 0 for a failed match
-and -1 for an internal error: typically a memory allocation failure.
+and -1 for an internal error: typically a memory allocation failure
+or an ASN.1 decoding error.
 
-X509_check_ip_asc() can also return -2 if the IP address string is malformed.
+All functions can also return -2 if the input is malformed. For example,
+X509_check_host() returns -2 if the provided B<name> contains embedded
+NULs.
 
 =head1 NOTES