diff --git a/wp-includes/media.php b/wp-includes/media.php
index 0a8621d209..f79ce679f6 100644
--- a/wp-includes/media.php
+++ b/wp-includes/media.php
@@ -1366,13 +1366,17 @@ function wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attac
 	 * (which is to say, when they share the domain name of the current request).
 	 */
 	if ( is_ssl() && ! str_starts_with( $image_baseurl, 'https' ) ) {
-		// Since the `Host:` header might contain a port we should
-		// compare it against the image URL using the same port.
+		/*
+		 * Since the `Host:` header might contain a port, it should
+		 * be compared against the image URL using the same port.
+		 */
 		$parsed = parse_url( $image_baseurl );
-		$domain = $parsed['host'];
+		$domain = isset( $parsed['host'] ) ? $parsed['host'] : '';
+
 		if ( isset( $parsed['port'] ) ) {
 			$domain .= ':' . $parsed['port'];
 		}
+
 		if ( $_SERVER['HTTP_HOST'] === $domain ) {
 			$image_baseurl = set_url_scheme( $image_baseurl, 'https' );
 		}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 4dd61bb5c2..efbab7728c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-alpha-58772';
+$wp_version = '6.7-alpha-58773';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.