diff --git a/src/internal.c b/src/internal.c
index 44cca779c..5d6a8fe3a 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -10168,23 +10168,22 @@ int CheckForAltNames(DecodedCert* dCert, const char* domain, int* checkCN)
 #if defined(OPENSSL_ALL) || defined(WOLFSSL_IP_ALT_NAME)
         /* check if alt name is stored as IP addr octet */
         if (altName->type == ASN_IP_TYPE) {
-            char tmp[4];
-            int i;
-            word32 idx = 0;
-            for (i = 0; (idx < WOLFSSL_MAX_IPSTR) && (i < altName->len); i++) {
-                XMEMSET(tmp, 0, sizeof(tmp));
-                XSNPRINTF(tmp, sizeof(tmp), (altName->len <= 4) ? "%u" : "%02X",
-                        altName->name[i]);
-                idx += (word32)XSTRLEN(tmp);
-                XSTRNCAT(name, tmp, (altName->len <= 4) ? 3 : 2);
-                if ((idx < WOLFSSL_MAX_IPSTR ) && ((i + 1) < altName->len)) {
-                    name[idx++] = (altName->len <= 4) ? '.' : ':';
+            const unsigned char *ip = (const unsigned char*)altName->name;
+            if (altName->len == WOLFSSL_IP4_ADDR_LEN) {
+                XSNPRINTF(name, sizeof(name), "%u.%u.%u.%u", ip[0], ip[1], ip[2], ip[3]);
+            }
+            else if (altName->len == WOLFSSL_IP6_ADDR_LEN) {
+                int i;
+                for (i = 0; i < 8; i++) {
+                    XSNPRINTF(name + i * 5, sizeof(name) - i * 5, "%02X%02X%s",
+                              ip[2 * i], ip[2 * i + 1], (i < 7) ? ":" : "");
                 }
             }
-            if (idx >= WOLFSSL_MAX_IPSTR) {
-                idx = WOLFSSL_MAX_IPSTR -1;
+            else {
+                WOLFSSL_MSG("\tnot an IPv4 or IPv6 address");
+                altName = altName->next;
+                continue;
             }
-            name[idx] = '\0';
             buf = name;
             len = (word32)XSTRLEN(name);
         }
diff --git a/tests/api.c b/tests/api.c
index 8786331f5..0f3b0024c 100644
--- a/tests/api.c
+++ b/tests/api.c
@@ -32975,9 +32975,15 @@ static void test_wolfSSL_X509_sign(void)
                 ASN_DNS_TYPE), SSL_SUCCESS);
 #if defined(OPENSSL_ALL) || defined(WOLFSSL_IP_ALT_NAME)
     {
-        unsigned char ip_type[] = {127,0,0,1};
-        AssertIntEQ(wolfSSL_X509_add_altname_ex(x509, (char*)ip_type,
-                sizeof(ip_type), ASN_IP_TYPE), SSL_SUCCESS);
+        unsigned char ip4_type[] = {127,128,0,255};
+        unsigned char ip6_type[] = {0xdd, 0xcc, 0xba, 0xab,
+                                    0xff, 0xee, 0x99, 0x88,
+                                    0x77, 0x66, 0x55, 0x44,
+                                    0x00, 0x33, 0x22, 0x11};
+        AssertIntEQ(wolfSSL_X509_add_altname_ex(x509, (char*)ip4_type,
+                sizeof(ip4_type), ASN_IP_TYPE), SSL_SUCCESS);
+        AssertIntEQ(wolfSSL_X509_add_altname_ex(x509, (char*)ip6_type,
+                sizeof(ip6_type), ASN_IP_TYPE), SSL_SUCCESS);
     }
 #endif
 #endif /* WOLFSSL_ALT_NAMES */
@@ -32994,7 +33000,8 @@ static void test_wolfSSL_X509_sign(void)
     AssertIntEQ(X509_get_ext_count(x509), 1);
 #endif
 #if defined(WOLFSSL_ALT_NAMES) && (defined(OPENSSL_ALL) || defined(WOLFSSL_IP_ALT_NAME))
-    AssertIntEQ(wolfSSL_X509_check_ip_asc(x509, "127.0.0.1", 0), 1);
+    AssertIntEQ(wolfSSL_X509_check_ip_asc(x509, "127.128.0.255", 0), 1);
+    AssertIntEQ(wolfSSL_X509_check_ip_asc(x509, "DDCC:BAAB:FFEE:9988:7766:5544:0033:2211", 0), 1);
 #endif
 
     AssertIntEQ(wolfSSL_X509_get_serial_number(x509, sn, &snSz),
@@ -33016,8 +33023,8 @@ static void test_wolfSSL_X509_sign(void)
     /* Valid case - size should be 798-797 with 16 byte serial number */
     AssertTrue((ret == 781 + snSz) || (ret == 782 + snSz));
 #elif defined(OPENSSL_ALL) || defined(WOLFSSL_IP_ALT_NAME)
-    /* Valid case - size should be 935-936 with 16 byte serial number */
-    AssertTrue((ret == 919 + snSz) || (ret == 920 + snSz));
+    /* Valid case - size should be 955-956 with 16 byte serial number */
+    AssertTrue((ret == 939 + snSz) || (ret == 940 + snSz));
 #else
     /* Valid case - size should be 926-927 with 16 byte serial number */
     AssertTrue((ret == 910 + snSz) || (ret == 911 + snSz));
diff --git a/wolfssl/ssl.h b/wolfssl/ssl.h
index b4f5daea8..d9b0812fe 100644
--- a/wolfssl/ssl.h
+++ b/wolfssl/ssl.h
@@ -570,6 +570,8 @@ struct WOLFSSL_X509_STORE {
 #if defined(OPENSSL_ALL) || defined(OPENSSL_EXTRA) || \
     defined(WOLFSSL_WPAS_SMALL) || defined(WOLFSSL_IP_ALT_NAME)
     #define WOLFSSL_MAX_IPSTR 46 /* max ip size IPv4 mapped IPv6 */
+    #define WOLFSSL_IP4_ADDR_LEN 4
+    #define WOLFSSL_IP6_ADDR_LEN 16
 #endif /* OPENSSL_ALL || WOLFSSL_IP_ALT_NAME */
 
 #if defined(OPENSSL_EXTRA) || defined(WOLFSSL_WPAS_SMALL)