diff --git a/Sources/Url.php b/Sources/Url.php
index ae3421dfe3..11477ecadd 100644
--- a/Sources/Url.php
+++ b/Sources/Url.php
@@ -605,7 +605,15 @@ public function isWebsite(): bool
 	 */
 	public function isScheme(string|array $scheme): bool
 	{
-		return !empty($this->scheme) && \in_array($this->scheme, array_map('strval', (array) $scheme));
+		if (empty($this->scheme)) {
+			return false;
+		}
+
+		return \in_array(
+			strtolower($this->scheme),
+			array_map(fn($s) => strtolower((string) $s), (array) $scheme),
+			true,
+		);
 	}
 
 	/**