diff --git a/lib/urlapi.c b/lib/urlapi.c
index d92887bf88..9fd08890f3 100644
--- a/lib/urlapi.c
+++ b/lib/urlapi.c
@@ -520,7 +520,7 @@ UNITTEST int ipv4_normalize(struct dynbuf *host)
     int rc;
     curl_off_t l;
     if(*c == '0') {
-      if(c[1] == 'x') {
+      if(Curl_raw_tolower(c[1]) == 'x') {
         c += 2; /* skip the prefix */
         rc = curlx_str_hex(&c, &l, UINT_MAX);
         if(rc)
diff --git a/tests/libtest/lib1560.c b/tests/libtest/lib1560.c
index a62d9334b2..a69511d492 100644
--- a/tests/libtest/lib1560.c
+++ b/tests/libtest/lib1560.c
@@ -706,6 +706,7 @@ static const struct urltestcase get_url_list[] = {
   {"https://0xffffffff", "https://255.255.255.255/", 0, 0, CURLUE_OK},
   {"https://1.0x1000000", "https://1.0x1000000/", 0, 0, CURLUE_OK},
   {"https://0x7f.1", "https://127.0.0.1/", 0, 0, CURLUE_OK},
+  {"https://0X7F.1", "https://127.0.0.1/", 0, 0, CURLUE_OK},
   {"https://1.2.3.256.com", "https://1.2.3.256.com/", 0, 0, CURLUE_OK},
   {"https://10.com", "https://10.com/", 0, 0, CURLUE_OK},
   {"https://1.2.com", "https://1.2.com/", 0, 0, CURLUE_OK},
@@ -765,10 +766,12 @@ static const struct urltestcase get_url_list[] = {
   {"https://16843009", "https://1.1.1.1/", 0, 0, CURLUE_OK},
   {"https://0177.1", "https://127.0.0.1/", 0, 0, CURLUE_OK},
   {"https://0111.02.0x3", "https://73.2.0.3/", 0, 0, CURLUE_OK},
+  {"https://0111.02.0X3", "https://73.2.0.3/", 0, 0, CURLUE_OK},
   {"https://0111.02.0x3.", "https://73.2.0.3/", 0, 0, CURLUE_OK},
   {"https://0111.02.030", "https://73.2.0.24/", 0, 0, CURLUE_OK},
   {"https://0111.02.030.", "https://73.2.0.24/", 0, 0, CURLUE_OK},
   {"https://0xff.0xff.0377.255", "https://255.255.255.255/", 0, 0, CURLUE_OK},
+  {"https://0XFF.0XFF.0377.255", "https://255.255.255.255/", 0, 0, CURLUE_OK},
   {"https://1.0xffffff", "https://1.255.255.255/", 0, 0, CURLUE_OK},
   /* IPv4 numerical overflows or syntax errors will not normalize */
   {"https://a127.0.0.1", "https://a127.0.0.1/", 0, 0, CURLUE_OK},