diff --git a/src/MD_STD_IN.php b/src/MD_STD_IN.php
index 829ec56..fe7b4e6 100644
--- a/src/MD_STD_IN.php
+++ b/src/MD_STD_IN.php
@@ -233,8 +233,16 @@ final class MD_STD_IN {
         }
 
         // Check for valid schemes
-        if (MD_STD::startsWithAny($output, ['https://', 'http://', 'ftp://']) === false) {
-            throw new MDInvalidUrl("Invalid input URL");
+        try {
+            if (MD_STD::startsWithAny($output, ['https://', 'http://', 'ftp://']) === false) {
+                throw new MDInvalidUrl("Invalid input URL" . PHP_EOL . $output . PHP_EOL . strtolower($output));
+            }
+        }
+        catch (MDInvalidUrl $e) {
+            if (MD_STD::startsWithAny(strtolower($output), ['https://', 'http://', 'ftp://']) === true) {
+                $output = strtolower(substr($output, 0, 8)) . substr($output, 8);
+            }
+            else throw $e;
         }
 
         if (\str_contains($output, '.') === false) {
diff --git a/src/testing/MD_STD_TEST_PROVIDERS.php b/src/testing/MD_STD_TEST_PROVIDERS.php
index 4d3b2b2..bfb23a1 100644
--- a/src/testing/MD_STD_TEST_PROVIDERS.php
+++ b/src/testing/MD_STD_TEST_PROVIDERS.php
@@ -45,6 +45,7 @@ final class MD_STD_TEST_PROVIDERS {
 
         return [
             'Regular URL without path or query' => ['https://www.museum-digital.org', 'https://www.museum-digital.org'],
+            'URL with uppercase character in scheme' => ['Https://www.museum-digital.org', 'https://www.museum-digital.org'],
             'URL with cyrillic characters, HTML-encoded ' => [
                 'https://sr.wikipedia.org/wiki/%D0%91%D0%B5%D0%BE%D0%B3%D1%80%D0%B0%D0%B4',
                 'https://sr.wikipedia.org/wiki/%D0%91%D0%B5%D0%BE%D0%B3%D1%80%D0%B0%D0%B4',
@@ -98,6 +99,8 @@ final class MD_STD_TEST_PROVIDERS {
             ];
         }
 
+        $output['Mail address is too long'] = [str_repeat("a", 10000) . '@example.com'];
+
         return $output;
 
     }