diff --git a/programs/x509/cert_req.c b/programs/x509/cert_req.c
index 1772f87d9b..fe060f3d92 100644
--- a/programs/x509/cert_req.c
+++ b/programs/x509/cert_req.c
@@ -66,7 +66,7 @@ int main(void)
     "    output_file=%%s      default: cert.req\n"      \
     "    subject_name=%%s     default: CN=Cert,O=mbed TLS,C=UK\n"   \
     "    san=%%s              default: (none)\n"       \
-    "                        Comma-separated-list of values:\n"     \
+    "                        Semicolon-separated-list of values:\n"     \
     "                          DNS:value\n"            \
     "                          URI:value\n"            \
     "                          IP:value (Only IPv4 is supported)\n"             \
@@ -119,7 +119,7 @@ struct options {
 static void ip_string_to_bytes(const char *str, uint8_t *bytes, int maxBytes)
 {
     for (int i = 0; i < maxBytes; i++) {
-        bytes[i] = (uint8_t) strtoul(str, NULL, 16);
+        bytes[i] = (uint8_t) strtoul(str, NULL, 10);
         str = strchr(str, '.');
         if (str == NULL || *str == '\0') {
             break;
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index c8412fb0f8..717cd396a7 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -136,12 +136,12 @@ int main(void)
     "                            Possible values: 0, 1\n"   \
     "                            (Considered for v3 only)\n" \
     "    san=%%s                   default: (none)\n"       \
-    "                            Comma-separated-list of values:\n" \
+    "                            Semicolon-separated-list of values:\n" \
     "                             DNS:value\n"            \
     "                             URI:value\n"            \
     "                             RFC822:value\n"         \
     "                             IP:value (Only IPv4 is supported)\n" \
-    "                             DN:value\n"             \
+    "                             DN:list of comma separated key=value pairs\n"\
     "    authority_identifier=%%s default: 1\n"             \
     "                            Possible values: 0, 1\n"   \
     "                            (Considered for v3 only)\n" \
@@ -219,7 +219,7 @@ struct options {
 static void ip_string_to_bytes(const char *str, uint8_t *bytes, int maxBytes)
 {
     for (int i = 0; i < maxBytes; i++) {
-        bytes[i] = (uint8_t) strtoul(str, NULL, 16);
+        bytes[i] = (uint8_t) strtoul(str, NULL, 10);
         str = strchr(str, '.');
         if (str == NULL || *str == '\0') {
             break;